Metals

21 pages, 9987 KiB

Open AccessArticle

Thermo-Mechanical Study of TIG Welding of Ti-6Al-4V for Residual Stresses Considering Solid State Phase Transformation

by Jingang Liu, Jianyun Zheng, Bing Fu, Lei Bu, Ruiqi Li and Songye Liu

Metals 2023, 13(5), 1001; https://doi.org/10.3390/met13051001 - 22 May 2023

Cited by 2 | Viewed by 1156

To overcome the detrimental effect of residual stress in welded joints, which affects the overall performance of the welded structure, this paper studies the magnitude and distribution of residual stress after welding and local post-weld heat treatment (PWHT). The coupled thermo-metallurgical-mechanical model for [...] Read more.

To overcome the detrimental effect of residual stress in welded joints, which affects the overall performance of the welded structure, this paper studies the magnitude and distribution of residual stress after welding and local post-weld heat treatment (PWHT). The coupled thermo-metallurgical-mechanical model for welding 6 mm thick Ti-6Al-4V (TC4) titanium alloy plates was established, the evolution of the SSPT and its effect on the residual stress were quantitatively analyzed, and a parametric analysis of local PWHT was performed. The results demonstrated that there was good agreement between the numerical results and the experimental data. Due to the cooling rate reaching 327 °C/s, the volume fraction of α^、 in the fusion zone (FZ) reached 0.218 after welding and decreased by 90.83% after PWHT when the heating temperature was 700 °C. The peak value of the longitudinal residual stress can reach 686.4 MPa after welding with SSPT, which was 11.38% lower than that without SSPT, and it decreased by 65.6% after PWHT when the heating temperature was 900 °C. The research results demonstrate that SSPT has a significant effect on residual stress, and PWHT can obviously reduce the residual stress, which provides a certain reference for welding TC4 titanium alloy plates. Full article

(This article belongs to the Special Issue Numerical Simulation of Metals Welding Process)

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29 pages, 11088 KiB

Open AccessArticle

Post-Weld Heat Treatment of S690QL1 Steel Welded Joints: Influence on Microstructure, Mechanical Properties and Residual Stress

by Damir Tomerlin, Dejan Marić, Dražan Kozak and Ivan Samardžić

Metals 2023, 13(5), 999; https://doi.org/10.3390/met13050999 - 21 May 2023

Cited by 3 | Viewed by 2224

Abstract

During the manufacturing of welded structures, some degree of residual stresses occurs. The classic approach to residual stress reduction is Post-Weld Heat Treatment (PWHT). In the case of structural grade mild steels, the thermal process is well established. In case of S690QL1 High [...] Read more.

During the manufacturing of welded structures, some degree of residual stresses occurs. The classic approach to residual stress reduction is Post-Weld Heat Treatment (PWHT). In the case of structural grade mild steels, the thermal process is well established. In case of S690QL1 High Strength Steel (HSS), which is manufactured using the Quenching and Tempering (QT) process considered in this paper, only limited PWHT treatment is possible without deterioration of mechanical properties. Since this steel grade is susceptible to subsequent heat input, the challenge is to establish adequate PWHT parameters, achieving residual stress reduction while retaining sufficiently high mechanical properties. The paper considers X joint welded HSS steel plates with slightly overmatching filler metal. The welded coupon is prepared and subjected to PWHT treatment. The research on the influence of heat treatment was performed using the four different PWHT cycles and initial As-Welded (AW) material condition. The authors proposed those PWHT cycles based on available resources and the literature. Process holding temperature is considered the variable parameter directly related to the behaviors of material properties. The methodology of welded joint analysis includes experimental testing of mechanical properties, metallographic examination, and residual stress quantification. Testing of mechanical properties includes tensile testing, Charpy V-notch impact testing, and hardness testing in scope of complete welded joint (BM + HAZ + WM). Metallographic examination is performed in order to characterize the welded joint material in relation to applied PWHT cycles. In order to quantify residual stresses, all heat-treated samples were examined via the X-ray diffraction method. Mechanical properties testing determined that an increase in PWHT cycle holding temperature leads to degradation of tested mechanical properties. For specific zones of the welded joint, the decreasing trend from AW condition to Cycle D (max. 600 °C) can be quantified. Based on representative specimens comparison, strength values (BM ≤ 5.7%, WM ≤ 12.1%, HAZ ≤ 20%), impact testing absorbed energy (BM = 17.1%, WM = 25.8%, FL = 12.5%, HAZ = 0.6%), and hardness values (BM = 4.1%, WM = 3.2%, CGHAZ = 16.6%, HAZ = 24.2%) are all exhibiting decrease. Metallographic examination, using the light microscopy, after the exposure to PWHT thermal cycles, did not reveal significant changes in the material throughout all specific welded joint segments. Average relative reduction in residual stress in correlation with PWHT temperature can be observed (AW = 0%, Cycle A (max. 400 °C) = 72%, Cycle B (max. 530 °C) = 81%, Cycle C (max. 550 °C) = 93% and Cycle D (max. 600 °C) = 100% stress reduction). It can be concluded that S690QL1 HSS welded joints can generally be subjected to PWHT, while adhering to the limits of the material and process. In the authors’ shared opinion, it is advisable to use the PWHT Cycle C (max. 550 °C) with 93% RS reduction, while mechanical properties retain high values. Full article

(This article belongs to the Special Issue Welding of Modern High-Strength Steels — Correlations between Process, Structure and Joint Properties)

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17 pages, 8104 KiB

Open AccessArticle

T15 High Speed Steels Produced by High-Temperature Low-Pressure Short-Time Vacuum Hot-Pressing Combined with Subsequent Diffusion-Bonding Treatment

by Wentao Shan and Yaojun Lin

Metals 2023, 13(5), 998; https://doi.org/10.3390/met13050998 - 21 May 2023

Cited by 1 | Viewed by 1357

Abstract

Currently, hot isostatic pressing (HIP) is widely used to produce highly alloyed high speed steels (HSSs) in an industrial scale; however, the HIP’s production cost is very high. Another powder consolidation approach with low production cost, namely vacuum hot-pressing (VHP), has hitherto received [...] Read more.

Currently, hot isostatic pressing (HIP) is widely used to produce highly alloyed high speed steels (HSSs) in an industrial scale; however, the HIP’s production cost is very high. Another powder consolidation approach with low production cost, namely vacuum hot-pressing (VHP), has hitherto received limited attention. The present work aims to develop an innovative solid-state VHP approach, producing HSSs with large cross-sectional sizes via a VHP facility having low loading capacity, thus further decreasing production cost. In doing so, VHP is performed at a sufficiently high temperature such that the pressure leading to full densification can be significantly reduced to a magnitude as low as several MPa; simultaneously, VHP is completed within a timeframe as short as several seconds to minutes, retaining fine carbide sizes; subsequently, the as-VHP HSS is diffusion-bonding treated (DBT-ed) at a relatively low temperature, achieving full metallurgical bond between powders while minimizing carbide growth. In the present work, T15 HSS was processed using the above VHP approach. The VHP temperature as high as 1200 °C was selected and consequently, the minimal pressure leading to full densification was decreased to ~7 MPa. By controlling displacement of pressing punch to a value corresponding to full densification, the VHP was competed for only 15 min. The almost fully dense as-VHP T15 HSS exhibits submicrometric carbide sizes smaller than those in the as-HIP counterpart, but incomplete metallurgical bond between powders. After diffusion bonding treatment at a relatively low temperature of 1100 °C for 2–4 h, the extent of metallurgical bond between powders is significantly enhanced with insignificant carbide growth. After regular quenching and tempering, the VHP plus DBT-ed T15 HSSs exhibit smaller average primary carbide sizes and similar hardness and three-point bend fracture strength, relative to those in the HIP counterpart after similar quenching and tempering. Full article

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13 pages, 2529 KiB

Open AccessCommunication

Data-Driven Inverse Problem for Optimizing the Induction Hardening Process of C45 Spur-Gear

by Sevan Garois, Monzer Daoud and Francisco Chinesta

Metals 2023, 13(5), 997; https://doi.org/10.3390/met13050997 - 21 May 2023

Cited by 3 | Viewed by 1124

Abstract

Inverse problems can be challenging and interesting to study in the context of metallurgical processes. This work aims to carry out a method for inverse modeling for simultaneous double-frequency induction hardening process. In this investigation, the experimental measured hardness profiles were considered as [...] Read more.

Inverse problems can be challenging and interesting to study in the context of metallurgical processes. This work aims to carry out a method for inverse modeling for simultaneous double-frequency induction hardening process. In this investigation, the experimental measured hardness profiles were considered as input data, while the output data were the process parameters. For this purpose experiments were carried out on C45 steel spur-gear. The method is based on machine learning algorithms and data treatment for dealing with inverse approach issues. In addition to the inverse modeling, a forward problem-based verification completes the study. It was found that according to promising results that this method is suitable and applicable for inverse problem of hardness modeling. Full article

(This article belongs to the Section Computation and Simulation on Metals)

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19 pages, 1777 KiB

Open AccessArticle

Estimation of Component Activities and Molar Excess Gibbs Energy of 19 Binary Liquid Alloys from Partial Pair Distribution Functions in Literature

by Chunlong Wang, Xiumin Chen and Dongping Tao

Metals 2023, 13(5), 996; https://doi.org/10.3390/met13050996 - 21 May 2023

Cited by 3 | Viewed by 1295

Abstract

This work proposes a new method for estimating the molar excess Gibbs energy and activity of liquid alloy based on recent research. The local composition theory provides a connection between the structures of liquid alloys and the thermodynamic models. The partial pair distribution [...] Read more.

This work proposes a new method for estimating the molar excess Gibbs energy and activity of liquid alloy based on recent research. The local composition theory provides a connection between the structures of liquid alloys and the thermodynamic models. The partial pair distribution function (PPDF) was utilized to calculate the parameters of the MIVM, RSM, Wilson, and NRTL. The statistics of the number of molecular pairs of MIVM and RSM were rewritten, which resulted in new forms of the two models. To enhance the NRTL’s estimation performance, the coordination number was incorporated into it (M-NRTL). The aforementioned model and Quasi-chemical model (QCM) were utilized to estimate the excess Gibbs energy and activity of 19 alloys. The alloys contained multiple sets of PPDFs, which enabled the calculation of multiple sets of model parameters. The work examined the impact of expressing the model parameters as first-order linear functions of the components or as constants on the accuracy of the estimation. The parameters were treated as constants. MIVM, RSM, and M-NRTL provided an average relative deviation (ARD) of activity of less than ±20% for 15, 10, and 9 alloys by estimation. When model parameters were expressed as a function of components, QCM showed the best estimation performance, having nine alloys with an ARD of less than ±20%. The number of alloys with an ARD of less than ±20% corresponding to MIVM, RSM, Wilson, NRTL, and M-NRTL was six, five, three, five, and two, respectively. This new method offers simplicity, numerical calculation stability, and excellent reproducibility. Full article

(This article belongs to the Special Issue Computational Modeling of Alloys)

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13 pages, 9623 KiB

Open AccessEditor’s ChoiceArticle

Effect of Tropical Marine Atmospheric Environment on Corrosion Behaviour of the 7B04-T74 Aluminium Alloy

by Ning Li, Weifang Zhang, Xiaojun Yan, Meng Zhang, Lu Han and Yikun Cai

Metals 2023, 13(5), 995; https://doi.org/10.3390/met13050995 - 21 May 2023

Cited by 2 | Viewed by 1706

Abstract

In this work, the effects of the tropical marine atmospheric environment on the corrosion behaviour of the 7B04-T74 aluminium alloy were systematically investigated by using accelerated testing, together with corrosion kinetic analysis, microstructure observation, product composition analysis, and potentiodynamic polarization curve tests. The [...] Read more.

In this work, the effects of the tropical marine atmospheric environment on the corrosion behaviour of the 7B04-T74 aluminium alloy were systematically investigated by using accelerated testing, together with corrosion kinetic analysis, microstructure observation, product composition analysis, and potentiodynamic polarization curve tests. The weight loss method was used for the corrosion kinetics analysis. The surface morphology and corrosion products transformation law were investigated by OM, SEM, EDS, and XPS. The electrochemical characteristics were studied using potentiodynamic polarization curves. The research indicated that the 7B04-T74 aluminium alloy has eminent corrosion resistance in the tropical marine atmospheric environment. Localized pitting corrosion occurred rapidly in the tropical marine atmosphere. In the later stage of corrosion, the corrosion of aluminium alloy did not become serious. Specifically, no obvious intergranular corrosion was found, which is related to the thermal treatment method. Corrosion products included Al(OH)₃, Al₂O₃, and AlCl₃, of which Al(OH)₃ is the most notable. Full article

(This article belongs to the Special Issue Corrosion Prediction in Different Environment)

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13 pages, 14900 KiB

Open AccessArticle

Effects of Mold Temperature on the Microstructures and Tensile Properties of the Thixoforged Graphite/AZ91D Composite

by Kejian Geng, Haipeng Jiang, Suqing Zhang, Xin Gao, Jianhua Wu, Cuicui Sun, Jixue Zhou and Xinfang Zhang

Metals 2023, 13(5), 1000; https://doi.org/10.3390/met13051000 - 21 May 2023

Viewed by 1058

Abstract

The effects of mold temperatures on the microstructures and mechanical properties of thixoforged Grp (graphite particles)/AZ91D composites have been investigated, followed by partial remelting and thixoforging technology. The results indicate that the best semi-solid microstructure could be obtained after being partially remelted at [...] Read more.

The effects of mold temperatures on the microstructures and mechanical properties of thixoforged Grp (graphite particles)/AZ91D composites have been investigated, followed by partial remelting and thixoforging technology. The results indicate that the best semi-solid microstructure could be obtained after being partially remelted at 600 °C and held for 60 min. Correspondingly, under a mold temperature of 300 °C, the best tensile properties were obtained by thixoforging. The UTS (ultimate tensile strength) and elongation of the thixoforged Grp/AZ91D were up to 304.1 MPa and 13.9%, respectively, which increased 11.3% and 43.1% in comparison with the thixoforged AZ91D, respectively. The variation of the tensile properties responded to the influences of mold temperatures on the amount of eutectic phase, the distribution of Grp, and the grain size of α-Mg. Meanwhile, HRTEM (High Resolution Transmission Electron Microscope) showed good bonding between Grp and AZ91D, and many edge dislocations were found in the inverse FFT (Fast Fourier Transform) image. And the result showed that the increase in tensile properties is attributed to the synergistic effect of load transfer, dislocation strengthening, and Orowan looping mechanisms from the Grp strengthening the matrix. Full article

(This article belongs to the Special Issue Advance of Carbon Reinforced Metal-Matrix Composites)

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18 pages, 6818 KiB

Open AccessArticle

Plasticity and Ductile Fracture of High-Strength Steel Center-Holed Plates under Tension

by Zhijuan Tian, Fei Yang, Sihao Wang, Zhuo Liu and Ao Chen

Metals 2023, 13(5), 994; https://doi.org/10.3390/met13050994 - 20 May 2023

Viewed by 1138

Abstract

The mechanical behavior of bolted connections in high-strength (HS) steel structures is a matter of concern, since the less ductility compared to mild steels may affect the load transfer and stress distribution of bolted connections. Conducting advanced finite element (FE) analysis incorporating validated [...] Read more.

The mechanical behavior of bolted connections in high-strength (HS) steel structures is a matter of concern, since the less ductility compared to mild steels may affect the load transfer and stress distribution of bolted connections. Conducting advanced finite element (FE) analysis incorporating validated material plasticity and ductile fracture criterion allows for a deeper understanding for the load transfer mechanism of HS steel joints. This paper focused on the plasticity and ductile fracture behaviors of HS (S700MC and S960Q) center-holed (CH) plates under tension, which are the essential component in bolted connections. Firstly, a combined linear and power law was used to calibrate and describe the post-necking stress–strain relations of the investigated HS steels. Then, a void-growth-model based on Rice–Tracey criterion was used to simulate the ductile fracture of five groups of CH plates with different hole diameters. The tensile strength and deformation capacity of the CH plates were discussed. The results showed that S700MC had a strain-hardening plasticity until the tensile fracture, while S960Q had a strain-hardening plasticity with a strain-softening behavior followed near the tensile fracture. Incorporating the calibrated plasticity and ductile fracture criterion in FE analyses generated close force-displacement curves as the experimental results. The equation specified in Eurocode produced conservative predictions for the net cross-sectional tensile strength of the investigated HS steels. Full article

(This article belongs to the Section Metal Failure Analysis)

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13 pages, 3724 KiB

Open AccessArticle

Influence of the Anodizing Time on the Microstructure and Immersion Stability of Tartaric-Sulfuric Acid Anodized Aluminum Alloys

by Florian Raffin, Jacques Echouard and Polina Volovitch

Metals 2023, 13(5), 993; https://doi.org/10.3390/met13050993 - 20 May 2023

Cited by 4 | Viewed by 1699

Abstract

Tartaric-sulfuric acid anodizing (TSA) has been selected by the aerospace industry to replace Cr(VI)-based anodizing treatments of aluminum alloys. Modification of the bath composition can result in the necessity to revise the process conditions, including the time necessary to obtain the desired properties [...] Read more.

Tartaric-sulfuric acid anodizing (TSA) has been selected by the aerospace industry to replace Cr(VI)-based anodizing treatments of aluminum alloys. Modification of the bath composition can result in the necessity to revise the process conditions, including the time necessary to obtain the desired properties of the anodized layer. This study focuses on the microstructure and immersion stability of the pilot scale anodized AA2024 aluminum alloy, with anodizing times of 25 min and 45 min. The layer structure was characterized by scanning electron microscopy (SEM) and glow discharge optical emission spectrometry (GD-OES). The electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion resistance and immersion stability of the samples in 0.01 M NaCl solution. The density of pores formed in the 45 min anodized samples was higher which correlated with higher impedance modulus at equivalent immersion time and higher thickness of the oxide layer. Contact angle measurements demonstrated better wettability of the 45 min anodized sample. The results suggest that 45 min anodizing offers higher corrosion resistance and better initial adhesion with subsequent post-treatment such as sealing or painting. Full article

(This article belongs to the Special Issue Corrosion and Protection of Lightweight Engineering Materials: Mg Alloys, Al Alloys, Ti Alloys and Other Related Metals)

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13 pages, 2820 KiB

Open AccessArticle

Hydrogen Solid State Storage on MgH₂ Compacts for Mass Applications

by Daniel Fruchart, Michel Jehan, Nataliya Skryabina and Patricia de Rango

Metals 2023, 13(5), 992; https://doi.org/10.3390/met13050992 - 20 May 2023

Cited by 3 | Viewed by 2256

Abstract

The mass storage of hydrogen is a challenge considering large industrial applications and continuous distribution, e.g., for domestic use as a future energy carrier that respects the environment. For a long time, molecular hydrogen was stored and distributed, either as a gas (pressurized [...] Read more.

The mass storage of hydrogen is a challenge considering large industrial applications and continuous distribution, e.g., for domestic use as a future energy carrier that respects the environment. For a long time, molecular hydrogen was stored and distributed, either as a gas (pressurized up to 75 MPa) or as a cryogenic liquid (20.4 K). Furthermore, the atomic storage of hydrogen in the solid-state form via metallic or covalent compounds is still the subject of intense research and limited to a small scale for some practical developments. In addition, other type H chemical storage routes are being tested, such as ammonia and LOHC (Liquid Organic Hydrogen Carrier), etc. In any case, the main constraint remains security. However, Hydrogen Solid State Storage (HSSS) using MgH₂ bodies has been shown to be feasible in terms of process and safety. Furthermore, its intrinsic volumetric densification was proven to be much better performing with 106:70:45 kgH₂/m³ for solid (RT):LH (20.4 K):gas (75 MPa), respectively. Very early on, fairly reactive MgH₂-based pellets were produced (for max. ~27 tons/year) at McPhy Energy using a series of unique and self-built installations. Thus, the design of large instrumented reservoirs was undertaken thanks to fundamental research first carried out at the CNRS. So, prototypes of storage units from 100 to ~5500 kWh have been produced. However, McPhy took other routes a few years ago (smelting and refueling stations) because the HSSS market was not merging at that time. Today, a new operator, Jomi–Leman, therefore, decided to try the challenge again focusing on applications with on-site production and mass HSSS. Full article

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14 pages, 39992 KiB

Open AccessArticle

Effects of HIP Process Parameters on Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by SLM

by Zhoujin Lv, Haofeng Li, Lida Che, Shuo Chen, Pengjie Zhang, Jing He, Zhanfang Wu, Shanting Niu and Xiangyang Li

Metals 2023, 13(5), 991; https://doi.org/10.3390/met13050991 - 20 May 2023

Cited by 3 | Viewed by 1651

Abstract

Ti-6Al-4V titanium alloy products formed by selective laser melting (SLM) are characterized by high strength and low plasticity. In addition, there may be pores inside the material, which may become a fracture sprouting point and accelerate the failure of the parts. Using an [...] Read more.

Ti-6Al-4V titanium alloy products formed by selective laser melting (SLM) are characterized by high strength and low plasticity. In addition, there may be pores inside the material, which may become a fracture sprouting point and accelerate the failure of the parts. Using an optical microscope (OM), scanning electron microscope (SEM), and electronic universal testing machine, the effects of hot isostatic pressing (HIP) parameters on the microstructure and tensile property of SLM-formed Ti-6Al-4V titanium alloy were investigated. The results show that HIP performed below the β-phase transition temperature, and the structure of the Ti-6Al-4V titanium alloy is composed of an α phase and β phase. With the increase in the HIP temperature, the α lath coarsens into a short rod, the content of the β phase increases and coarsens, and the tensile strength and yield strength of Ti-6Al-4V show a decreasing trend. With an HIP process performed at a temperature of 910 °C and pressure of 130 MPa for 2 h, the Ti-6Al-4V titanium alloy obtains the best matching of strength and plasticity. Full article

(This article belongs to the Special Issue Titanium Alloys: Microstructure, Deformation and Mechanical Properties)

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14 pages, 2518 KiB

Open AccessArticle

Automatic Detection of Sorbite Content in High Carbon Steel Wire Rod

by Xiaolin Zhu, Ling Qian, Qiang Yao, Guanxi Huang, Fan Xu, Xue Chen and Zhengjun Yao

Metals 2023, 13(5), 990; https://doi.org/10.3390/met13050990 - 20 May 2023

Cited by 1 | Viewed by 1189

Abstract

This paper presents a method for the automatic detection of sorbite content in high-carbon steel wire rods. A semantic segmentation model of sorbite based on DeepLabv3+ is established. The sorbite structure is segmented, and the prediction results are analyzed and counted based on [...] Read more.

This paper presents a method for the automatic detection of sorbite content in high-carbon steel wire rods. A semantic segmentation model of sorbite based on DeepLabv3+ is established. The sorbite structure is segmented, and the prediction results are analyzed and counted based on the metallographic images of high-carbon steel wire rods marked manually. For the problem of sample imbalance, the loss function of Dice loss + focal loss is used, and the perturbation processing of training data is added. The results show that this method can realize the automatic statistics of sorbite content. The average pixel prediction accuracy is as high as 94.28%, and the average absolute error is only 4.17%. The composite application of the loss function and the enhancement of the data perturbation significantly improve the prediction accuracy and robust performance of the model. In this method, the detection of sorbite content in a single image only takes 10 s, which is 99% faster than that of 10 min using the manual cut-off method. On the premise of ensuring detection accuracy, the detection efficiency is significantly improved and the labor intensity is reduced. Full article

(This article belongs to the Topic Microstructure and Properties in Metals and Alloys)

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15 pages, 10273 KiB

Open AccessArticle

Modified Voce-Type Constitutive Model on Solid Solution State 7050 Aluminum Alloy during Warm Compression Process

by Haihao Teng, Yufeng Xia, Chenghai Pan and Yan Li

Metals 2023, 13(5), 989; https://doi.org/10.3390/met13050989 - 19 May 2023

Cited by 1 | Viewed by 943

Abstract

The 7050 alloy is a kind of Al-Zn-Mg-Cu alloy that is widely used for aircraft structures. Although the deformation behavior of the solid solution state 7050 aluminum alloy is critical for engineering and manufacturing design, it has received little attention. In this study, [...] Read more.

The 7050 alloy is a kind of Al-Zn-Mg-Cu alloy that is widely used for aircraft structures. Although the deformation behavior of the solid solution state 7050 aluminum alloy is critical for engineering and manufacturing design, it has received little attention. In this study, the room and warm compression behavior of the solid solution-state 7050 alloy was researched, and a modified model with variable parameters was built for the flow stress and load prediction. The isothermal compression tests of the solid solution-state 7050 alloy were performed under the conditions of a deformation temperature of 333–523 K, a strain rate of 10⁻³–10⁻¹ s⁻¹, and a total reduction of 50%. The strain-stress curves at different temperatures were corrected by considering interface friction. The flow stress model of aluminum was established using the modified Voce model. For evaluating the modified Voce model’s prediction accuracy, the flow stresses calculated by the model were compared with the experimental values. Consequently, for assessing its prediction abilities in finite element applications, the whole compression process was simulated in the finite element analysis platform. The results sufficiently illustrated that the modified Voce-type model can precisely predict the complex flow behaviors during warm compression. This study will guide the prediction of the warm compression load and the optimization of the heat treatment process of the alloy. Full article

(This article belongs to the Special Issue Aluminum Alloys and Aluminum-Based Matrix Composites)

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17 pages, 4334 KiB

Open AccessArticle

Influence of Severe Plastic Deformation by Extrusion on Microstructure, Deformation and Thermal Behavior under Tension of Magnesium Alloy Mg-2.9Y-1.3Nd

by Elena Legostaeva, Anna Eroshenko, Vladimir Vavilov, Vladimir A. Skripnyak, Nikita Luginin, Arsenii Chulkov, Alexander Kozulin, Vladimir V. Skripnyak, Juergen Schmidt, Alexey Tolmachev, Pavel Uvarkin and Yurii Sharkeev

Metals 2023, 13(5), 988; https://doi.org/10.3390/met13050988 - 19 May 2023

Cited by 2 | Viewed by 1225

Abstract

The microstructural investigation, mechanical properties, and accumulation and dissipation of energies of the magnesium alloy Mg-2.9Y-1.3Nd in the recrystallized state and after severe plastic deformation (SPD) by extrusion are presented. The use of SPD provides the formation of a bimodal structure consisting of [...] Read more.

The microstructural investigation, mechanical properties, and accumulation and dissipation of energies of the magnesium alloy Mg-2.9Y-1.3Nd in the recrystallized state and after severe plastic deformation (SPD) by extrusion are presented. The use of SPD provides the formation of a bimodal structure consisting of grains with an average size 15 µm and of ultrafine-grained grains with sizes less than 1 µm and volume fractions up to 50%, as well as of the fine particles of the second Mg₂₄Y₅ phases. It is established that grain refinement during extrusion is accompanied by an increase of the yield strength, increase of the tensile strength by 1.5 times, and increase of the plasticity by 1.8 times, all of which are due to substructural hardening, redistribution of the phase composition, and texture formation. Using infrared thermography, it was revealed that before the destruction of Mg-2.9Y-1.3Nd in the recrystallized state, there is a sharp jump of temperature by 10 °C, and the strain hardening coefficient becomes negative and amounts to (−6) GPa. SPD leads to a redistribution of thermal energy over the sample during deformation, does not cause a sharp increase in temperature, and reduces the strain hardening coefficient by 2.5 times. Full article

(This article belongs to the Special Issue Thermomechanical Treatment of Metals and Alloys)

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24 pages, 10897 KiB

Open AccessArticle

Offline Feed-Rate Scheduling Method for Ti–Al Alloy Blade Finishing Based on a Local Stiffness Estimation Model

by Long Wu, Aimin Wang and Wenhao Xing

Metals 2023, 13(5), 987; https://doi.org/10.3390/met13050987 - 19 May 2023

Viewed by 975

Abstract

In the aerospace field, Ti–Al alloy thin-walled parts, such as blades, generally undergo a large amount of material removal and have a low processing efficiency. Scheduling the feed rate during machining can significantly improve machining efficiency. However, existing feed-rate scheduling methods rarely consider [...] Read more.

In the aerospace field, Ti–Al alloy thin-walled parts, such as blades, generally undergo a large amount of material removal and have a low processing efficiency. Scheduling the feed rate during machining can significantly improve machining efficiency. However, existing feed-rate scheduling methods rarely consider the influence of machining deformation factors and cannot be applied in the finishing stages of thin-walled parts. This study proposes an offline feed-rate scheduling method based on a local stiffness estimation model that can be used to reduce machining errors and improve efficiency in the finishing stage of thin-walled parts. In the proposed method, a predictive model that can rapidly calculate the local stiffness at each cutter location point and a cutting-force prediction model that considers the effect of cutting angle are established. Based on the above model, an offline feed-rate scheduling method that considers machining deformation error constraints is introduced. Finally, an experiment is performed by taking the finishing of actual blade parts as an example. The experimental results demonstrate that the proposed feed-rate scheduling method can improve the machining efficiency of parts while ensuring machining accuracy. The proposed method can also be conveniently applied to feed-rate scheduling in the finishing stage of other thin-walled parts without being limited by machine tools. Full article

(This article belongs to the Section Metal Matrix Composites)

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10 pages, 1644 KiB

Open AccessArticle

Laser Additive Manufacturing of Layered Zr-Based Bulk Metallic Glass Composite

by He Ma, Dandan Qin, Chun Shang and Yunzhuo Lu

Metals 2023, 13(5), 986; https://doi.org/10.3390/met13050986 - 19 May 2023

Cited by 1 | Viewed by 1197

Abstract

As a potential functional material, much effort has been devoted to enhancing the mechanical properties of bulk metallic glass composites (BMGCs). Among them, layered BMGCs are regarded as effective for achieving a strength–ductility synergistic effect. However, it is difficult with the existing metallic [...] Read more.

As a potential functional material, much effort has been devoted to enhancing the mechanical properties of bulk metallic glass composites (BMGCs). Among them, layered BMGCs are regarded as effective for achieving a strength–ductility synergistic effect. However, it is difficult with the existing metallic glass (MG) preparation technologies to obtain a decent layered structure. In addition, the fragile interface between layers formed using the traditional fabricating method always exacerbates the deterioration of mechanical properties, which restricts the wide application of layered BMGCs. In the case of laser additive manufacturing (LAM), the cooperation of coarse grains in the hot affected zone (HAZ) and fine grains in the remelting zone induced by a unique thermal history is of key importance in eliminating the fragile interface and therefore overcoming premature cracking. Thus, we successfully synthesized Nb-Zr₄₈Cu_46.5Al₄Nb_1.5 layered material with a yield strength of 1332 (±91) MPa and a compression ductility of 4.17 (±0.14)% via LAM. The results of the compressive curves of Nb and BMGC prepared by LAM decisively demonstrate that the layered material obtains a certain degree of plasticity while maintaining relatively high strength. This remarkable mechanical property is mainly attributed to the asynchronous deformation and the interaction of the adjacent Nb and MG layers. It is worth emphasizing that a distinctive round-way crack extension is discovered during the deformation process, which plays a significant role in breaking through the strength ductility trade-off. In addition, the source of yield strength is calculated theoretically using the rule of the mixture and the dislocation strengthening principle. The results indicate that the strength contributed by geometrically necessary dislocations is around 101.7 MPa. In addition, the strength calculated by the rule of the mixture is ~1201.9 MPa. This work offers a new paradigm for BMGCs with excellent strength and ductility as practical engineering materials. Full article

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18 pages, 5731 KiB

Open AccessArticle

Multi-Physical Field Coupling Simulation and Experiments with Pulse Electrochemical Machining of Large Size TiAl Intermetallic Blade

by Yudi Wang, Zhengyang Xu, Deman Meng, Lin Liu and Zhongdong Fang

Metals 2023, 13(5), 985; https://doi.org/10.3390/met13050985 - 19 May 2023

Cited by 2 | Viewed by 1030

Abstract

Large size TiAl alloy blade is one of the important parts to reduce the weight of advanced aero-engines. However, the precision manufacturing of such blades is a challenge due to their large size, low ductility at room temperature, and high hardness of the [...] Read more.

Large size TiAl alloy blade is one of the important parts to reduce the weight of advanced aero-engines. However, the precision manufacturing of such blades is a challenge due to their large size, low ductility at room temperature, and high hardness of the TiAl alloy. Electrochemical machining (ECM) is a very promising method for the precision manufacturing of such blades, considering its unique advantages. In this study, a very comprehensive multi-physical field coupling simulation and pulse ECM experiments on large size TiAl alloy blades are carried out. Geometric and theoretical models involving electric fields, gas-liquid two-phase flow, heat transfer, and anodic dissolution are developed. The variation of bubble, temperature, electrolyte flow rate, and electrical conductivity at the outlet and the different areas on the blade surface with the processing time and distribution along the flow channel in the machining gap are revealed by simulation. It is found that the influence of electrolyte temperature on electrical conductivity is more dominant than that of bubble concentration. Finally, the experiments of pulse ECM on large size TiAl alloy blade are carried out, and the experimental results are analyzed in detail. The high efficiency and high surface quality of large size TiAl alloy blades are realized. The surface roughness and machining accuracy of the blade are about Ra 0.9 μm and 0.18 mm, respectively. Full article

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15 pages, 12479 KiB

Open AccessArticle

Archaeometallurgical Characterization of Two Lombard Early Medieval Bloomery Slags from Ponte di Val Gabbia I Site (Northern Italy)

by Paolomarco Merico, Michela Faccoli, Daniele La Corte and Giovanna Cornacchia

Metals 2023, 13(5), 984; https://doi.org/10.3390/met13050984 - 19 May 2023

Viewed by 1136

Abstract

An archaeometallurgical characterization of two iron smelting tap slags recovered from the early medieval site of Ponte di Val Gabbia I (Brescia, northern Italy) was performed. The main goal was to infer from the slags the working conditions of the ancient bloomery furnace [...] Read more.

An archaeometallurgical characterization of two iron smelting tap slags recovered from the early medieval site of Ponte di Val Gabbia I (Brescia, northern Italy) was performed. The main goal was to infer from the slags the working conditions of the ancient bloomery furnace in terms of temperature and oxygen chemical potential. The petrology of both slags was investigated by light optical microscopy and scanning electron microscopy, while their chemical compositions were measured via scanning electron microscopy coupled with X-ray dispersive spectroscopy. High-resolution Raman micro-spectrometry was used to confirm the identification of the mineralogical phases. The software Rhyolite-MELTS was used to compute the liquidus temperatures of the two slags, which were found to be 1120 °C and 1146 °C. These temperatures approximate the working temperature of the bloomery furnace. A thermodynamic-based approach was adopted to estimate the redox conditions of the reducing atmosphere of the smelting furnace, revealing that the two slags formed in different redox environments. Specifically, the resulting oxygen chemical potentials were −382.61 kJ/mol and −243.80 kJ/mol at the liquidus temperatures of 1120 °C and 1146 °C, respectively. Full article

(This article belongs to the Special Issue Metals for Art and Cultural Heritage)

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13 pages, 25394 KiB

Open AccessArticle

Effects of L-PBF Scanning Strategy and Sloping Angle on the Process Properties of TC11 Titanium Alloy

by Xuben Lu, Chang Shu, Zhiyu Zheng, Xuedao Shu, Siyuan Chen, Khamis Essa, Zixuan Li and Haijie Xu

Metals 2023, 13(5), 983; https://doi.org/10.3390/met13050983 - 19 May 2023

Cited by 2 | Viewed by 1228

Abstract

TC11 titanium alloy is widely used in aerospace. To investigate the production of TC11 titanium alloy parts of high quality and performance, this paper adopts the Laser powder bed fusion (L-PBF) technique to prepare TC11 alloy specimens. We analyze in detail the effects [...] Read more.

TC11 titanium alloy is widely used in aerospace. To investigate the production of TC11 titanium alloy parts of high quality and performance, this paper adopts the Laser powder bed fusion (L-PBF) technique to prepare TC11 alloy specimens. We analyze in detail the effects of scanning strategy and forming angle on the forming quality and performance of TC11 alloy through a combination of theory and experiment. The results show that the upper surface quality of the strip-scanned molded parts is the highest, and the upper surface quality is better than that of the side surface under different scanning strategies. The fusion channel lap and surface adhesion powder were the main factors affecting the surface roughness. With increases in the forming angle, the surface roughness of the overhanging surface gradually decreases and the hardness gradually increases. The surface quality and hardness of the specimen are optimal when the forming angle is 90°. The research results provide the theoretical basis and technical support for L-PBF forming of TC11 titanium alloy parts. Full article

(This article belongs to the Special Issue Additive Manufacturing of Titanium Alloys 2022)

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11 pages, 1840 KiB

Open AccessEditor’s ChoiceArticle

Corrosion of Copper in a Tropical Marine Atmosphere Rich in H₂S Resulting from the Decomposition of Sargassum Algae

by Mahado Said Ahmed, Mounim Lebrini, Benoit Lescop, Julien Pellé, Stéphane Rioual, Olivia Amintas, Carole Boullanger and Christophe Roos

Metals 2023, 13(5), 982; https://doi.org/10.3390/met13050982 - 19 May 2023

Cited by 3 | Viewed by 1786

Abstract

The atmospheric corrosion of copper exposed in Martinique (Caribbean Sea) for 1 year was reported. This island suffered the stranding of sargassum algae, which decompose and release toxic gases such as hydrogen sulfide (H₂S) or ammonia (NH₃). Four sites [...] Read more.

The atmospheric corrosion of copper exposed in Martinique (Caribbean Sea) for 1 year was reported. This island suffered the stranding of sargassum algae, which decompose and release toxic gases such as hydrogen sulfide (H₂S) or ammonia (NH₃). Four sites in Martinique (France) more or less impacted by sargassum algae strandings were selected. The corrosion rate was studied via mass loss determination. The morphology and properties of the corrosion products were determined using Scanning Electron Microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The samples were exposed for up to 12 months. The mass loss results after 1-year exposure were from 4.8 µm for the least impacted site to 325 µm for the site most affected by sargassum algae. This very high value proves that the presence of sargassum algae caused a significant degradation of copper. The morphological structures and properties of the corrosion products obtained at the impacted and non-impacted sites differed significantly. In the absence of sargassum algae, classical corrosion products of copper were reported such as Cu₂O and Cu₂Cl(OH)₃. In the sites near the stranding of the sargassum algae, the CuS product is the main corrosion product obtained, but copper hydroxylsulfate is created. Full article

(This article belongs to the Section Corrosion and Protection)

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12 pages, 3164 KiB

Open AccessArticle

Copper Oxide Nitrogen-Rich Porous Carbon Network Boosts High-Performance Supercapacitors

by Dan Li, Hanhao Liu, Zijie Liu, Que Huang, Beihu Lu, Yanzhong Wang, Chao Wang and Li Guo

Metals 2023, 13(5), 981; https://doi.org/10.3390/met13050981 - 19 May 2023

Cited by 1 | Viewed by 1240

Abstract

Transition metal oxides with various valence states have high specific capacitance and have attracted much attention. However, the poor cycle stability caused by material agglomeration seriously limits the play of its high activity. Herein, we create a stress dispersion structure (Cu_xO [...] Read more.

Transition metal oxides with various valence states have high specific capacitance and have attracted much attention. However, the poor cycle stability caused by material agglomeration seriously limits the play of its high activity. Herein, we create a stress dispersion structure (Cu_xO composite porous carbon net) by in situ lyophilization and one-step carbonization, effectively anchoring highly reactive copper oxides and highly conductive carbon networks combined with high nitrogen doping of 10.7%, to investigate their electrochemical performance in supercapacitors. Specifically, the specific capacitance of Cu_xO@NPC can be as high as 392 F/g (0.5 A/g) in the three-electrode system with 6 mol/L KOH as electrolyte. When applied to the two-electrode system, the cycle stability of the whole device can reach 97% after 10,000 cycles. Full article

(This article belongs to the Special Issue Manufacturing and Characterization of Metallic Electrode Materials)

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4 pages, 189 KiB

Open AccessEditorial

Recent Advances in Cast Irons

by Annalisa Fortini and Chiara Soffritti

Metals 2023, 13(5), 980; https://doi.org/10.3390/met13050980 - 19 May 2023

Viewed by 1126

Abstract

Cast irons are widely used in industry due to their excellent castability, allowing for the production of near-net shape components with complex geometries without the need for additional forging or machining processes [...] Full article

(This article belongs to the Special Issue Recent Advances in Cast Irons)

21 pages, 6238 KiB

Open AccessReview

Review on Anti-Fatigue Performance of Gradient Microstructures in Metallic Components by Laser Shock Peening

by Fei Yang, Ping Liu, Liucheng Zhou, Weifeng He, Xinlei Pan and Zhibin An

Metals 2023, 13(5), 979; https://doi.org/10.3390/met13050979 - 18 May 2023

Cited by 5 | Viewed by 1313

Abstract

Laser-shock-peening technology is an international research hotspot in the surface-strengthening field, which utilizes the mechanical effects of laser-induced plasma shock waves to effectively improve the fatigue performance of metallic components by introducing the gradient microstructures and compressive residual stress into the surface layer [...] Read more.

Laser-shock-peening technology is an international research hotspot in the surface-strengthening field, which utilizes the mechanical effects of laser-induced plasma shock waves to effectively improve the fatigue performance of metallic components by introducing the gradient microstructures and compressive residual stress into the surface layer of processed materials. The fatigue failure caused by high-frequency vibrations in aeroengines during service is the most important threat to flight safety, and this case is more prominent for military aeroengines because their service situation is harsher. The present paper focuses on components such as high-temperature components, fan/compressor blade, and thin-walled weldments, and it systematically introduces the researching findings about surface nanocrystallization and compressive residual stress formation mechanism in typical aeronautical metallic materials treated by laser shock peening. The contents mainly involve the characteristics, formation process, fatigue resistance mechanism, thermal stability of residual compressive stress, and nanocrystallization generated by laser shock peening. Full article

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12 pages, 6316 KiB

Open AccessArticle

The Behavior of Direct Reduced Iron in the Electric Arc Furnace Hotspot

by Andreas Pfeiffer, Daniel Ernst, Heng Zheng, Gerald Wimmer and Johannes Schenk

Metals 2023, 13(5), 978; https://doi.org/10.3390/met13050978 - 18 May 2023

Cited by 2 | Viewed by 4086

Abstract

Hydrogen-based direct reduction is a promising technology for CO₂ lean steelmaking. The electric arc furnace is the most relevant aggregate for processing direct reduced iron (DRI). As DRI is usually added into the arc, the behavior in this area is of great [...] Read more.

Hydrogen-based direct reduction is a promising technology for CO₂ lean steelmaking. The electric arc furnace is the most relevant aggregate for processing direct reduced iron (DRI). As DRI is usually added into the arc, the behavior in this area is of great interest. A laboratory-scale hydrogen plasma smelting reduction (HPSR) reactor was used to analyze that under inert conditions. Four cases were compared: carbon-free and carbon-containing DRI from DR-grade pellets as well as fines from a fluidized bed reactor were melted batch-wise. A slag layer’s influence was investigated using DRI from the BF-grade pellets and the continuous addition of slag-forming oxides. While carbon-free materials show a porous structure with gangue entrapments, the carburized DRI forms a dense regulus with the oxides collected on top. The test with slag-forming oxides demonstrates the mixing effect of the arc’s electromagnetic forces. The cross-section shows a steel melt framed by a slag layer. These experiments match the past work in that carburized DRI is preferable, and material feed to the hotspot is critical for the EAF operation. Full article

(This article belongs to the Special Issue Electric Arc Furnace and Converter Steelmaking)

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18 pages, 8592 KiB

Open AccessReview

Research Progress on New Types of H₂TiO₃ Lithium-Ion Sieves: A Review

by Ying Li, Zhen Yang and Peihua Ma

Metals 2023, 13(5), 977; https://doi.org/10.3390/met13050977 - 18 May 2023

Cited by 2 | Viewed by 2193

Abstract

The advantages of new types of H₂TiO₃ lithium-ion sieves, including excellent adsorption performance, high-efficiency Li⁺-ion selectivity, reliable regeneration, environmental friendliness, and easy preparation, have attracted considerable attention. Currently, the prices of lithium carbonate and other related products are [...] Read more.

The advantages of new types of H₂TiO₃ lithium-ion sieves, including excellent adsorption performance, high-efficiency Li⁺-ion selectivity, reliable regeneration, environmental friendliness, and easy preparation, have attracted considerable attention. Currently, the prices of lithium carbonate and other related products are rapidly increasing, so the use of H₂TiO₃ lithium-ion sieves to extract lithium resources in salt lake brine has become a crucial strategy. H₂TiO₃ lithium-ion sieve is a layered double hydroxide with a 3R₁ sequence to arrange oxygen layers. Its adsorption mechanism involves the breaking of surface O-H bonds and the formation of O-Li bonds. This study provides a theoretical basis for developing high-efficiency lithium-ion sieves. This article also summarizes the influencing factors for the synthesis process of H₂TiO₃, which can seriously influence the adsorption performance, and offers experimental verification for the preparation of H₂TiO₃ lithium-ion sieves. H₂TiO₃ lithium-ion sieves prepared from anatase using a reasonable method show the largest adsorption capacity. In addition, effective ways to recycle H₂TiO₃ are outlined, which provide a guarantee for its industrial application. Finally, this paper summarizes the full text and points out future research directions for H₂TiO₃ lithium-ion sieves. Full article

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16 pages, 62638 KiB

Open AccessArticle

Surface Formation of Sloping Features in Laser Powder–Bed Fusion by Multi-Track Multi-Layer Simulations

by Trong-Nhan Le and Kevin Chou

Metals 2023, 13(5), 976; https://doi.org/10.3390/met13050976 - 18 May 2023

Cited by 2 | Viewed by 1395

Abstract

Laser powder–bed fusion (L-PBF) metal additive manufacturing has been widely utilized in various industries. However, large variability and inconsistent quality of the built parts still hinder the full potential of this manufacturing technology. Regarding part quality, the poor surface finish of sloping features [...] Read more.

Laser powder–bed fusion (L-PBF) metal additive manufacturing has been widely utilized in various industries. However, large variability and inconsistent quality of the built parts still hinder the full potential of this manufacturing technology. Regarding part quality, the poor surface finish of sloping features remains one of the major shortcomings of L-PBF. The process parameters and contouring strategies have been identified as the primary factors dictating the surface roughness of the inclined surfaces, both up-skin and down-skin. Experimental approaches to modify the surface roughness by tuning contouring parameters could be costly and time-consuming. In addition, such methods cannot provide adequate physical insights into the phenomenon. Therefore, this study presents a multi-physics modeling framework to simulate a multi-track multi-layer L-PBF process in fabricating an inclined sample. The established simulation provides a valuable physical understanding of the driving forces exacerbating the formation and roughness of the inclined surfaces. The simulation results imply that the voids, formed due to insufficient melting in the low-energy contouring scan, are the leading cause of higher surface roughness for up-skin regions. On the other hand, though the visualization of attached particles is challenging regarding the down-skin surface, the simulated results show a lower and abnormal thermal gradient at the melt boundary due to the poorly supported melt region. The presence of thermal gradient irregularities suggests an overabundance of powder particles adhering to the melt boundary, resulting in increased surface roughness on the down-skin. Full article

(This article belongs to the Special Issue Multi-Scale Modeling in Additive Manufacturing)

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15 pages, 13895 KiB

Open AccessArticle

Influence of Higher Stabilization Temperatures on the Microstructure and Mechanical Properties of Austenitic Stainless Steel 08Ch18N10T

by Tomáš Janda, Štěpán Jeníček, Ludmila Kučerová, Radek Leták, Dagmar Jandová and Hana Jirková

Metals 2023, 13(5), 975; https://doi.org/10.3390/met13050975 - 18 May 2023

Cited by 2 | Viewed by 1195

Abstract

Precipitation strengthening in titanium-stabilized austenitic stainless steels can improve the hot yield strength, as requested, e.g., for nuclear industry applications. The resulting properties depend mainly on the parameters of the heat treatment and previous forming. The influence of the heat treatment parameters on [...] Read more.

Precipitation strengthening in titanium-stabilized austenitic stainless steels can improve the hot yield strength, as requested, e.g., for nuclear industry applications. The resulting properties depend mainly on the parameters of the heat treatment and previous forming. The influence of the heat treatment parameters on the development of the microstructure and mechanical properties was determined for steel 08Ch18N10T (GOST). Solution annealing and stabilization with different temperatures and holds were performed on the steel, which was, in delivered condition, stabilized at 720 °C. Heat-treated samples were subjected to static tensile testing at room temperature and at 350 °C, microstructural analysis using light, scanning electron and transmission electron microscopy focused on precipitates, and HV10 hardness testing. The strengthening mechanism and its dependence on the stabilization parameters are described. The results of the experiment show the influence of the state of the input material on the final effect of heat treatment—repeated heat treatment achieved lower-strength characteristics than the initial state, while almost all modes showed above-limit values for the mechanical properties. Stabilization temperatures of 720 to 800 °C were found to be optimal in terms of the achieved hot yield strength. At higher temperatures, slightly lower strengths were achieved, but at significantly shorter dwell times. Full article

(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)

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20 pages, 12131 KiB

Open AccessArticle

Dynamic Modeling and Stability Prediction of Robot Milling Considering the Influence of Force-Induced Deformation on Regenerative Effect and Process Damping

by Yuchao Du, Zhiqiang Liang, Sichen Chen, Hao Huang, Haoran Zheng, Zirui Gao, Tianfeng Zhou, Zhibing Liu and Xibin Wang

Metals 2023, 13(5), 974; https://doi.org/10.3390/met13050974 - 18 May 2023

Viewed by 1329

Abstract

Undesirable chatter is one of the key problems that restrict the improvement of robot milling quality and efficiency. The prediction of chatter stability, which is used to guide the selection of process parameters, is an effective method to avoid chatter in robot milling. [...] Read more.

Undesirable chatter is one of the key problems that restrict the improvement of robot milling quality and efficiency. The prediction of chatter stability, which is used to guide the selection of process parameters, is an effective method to avoid chatter in robot milling. Due to the weak stiffness of the robot, deformation caused by milling forces becomes an unavoidable problem, which will change the tool–workpiece contact area and affect the stability prediction. However, it is often simplified and neglected. In this paper, a multipoint contact dynamic model of robot milling is established, which considers the influence of force-induced deformation on the regenerative effect and process damping. The tool–workpiece contact area is discretized into a finite number of nodes along the axial direction so that the force and deformation at each node can be calculated separately. The different contact forms of the tool–workpiece under different process parameters are discussed in different cases, and the interaction process between cutting force and force-induced deformation is analyzed in detail. An iterative strategy is used to calculate the deformation of each node and the result of the tool–workpiece contact boundary. Finally, chatter stability of robot milling is predicted by a fully discrete method. Robot milling experiments were carried out to verify the predicted results. The results show that force-induced deformation is an important factor improving the stability prediction accuracy of robot milling, and a more accurate prediction result can be obtained by simultaneously considering force-induced deformation and process damping. Full article

(This article belongs to the Special Issue High Performance Machining of Difficult-to-Process Metals)

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24 pages, 6210 KiB

Open AccessArticle

Machinability Comparison of TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN Coated Carbide Inserts in Turning Hardened AISI 4340 Steel Using Grey-Crow Search Hybrid Optimization

by Mohammed Al Awadh, Ramanuj Kumar, Oğur İynen, Mohammad Rafighi, Mustafa Özdemir and Anish Pandey

Metals 2023, 13(5), 973; https://doi.org/10.3390/met13050973 - 17 May 2023

Cited by 2 | Viewed by 1342

Abstract

This experimental study presents the machinability comparison of TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN coated carbide inserts in hard turning AISI 4340 steel. The primary purpose of this research is to determine the most appropriate cutting inserts in turning hardened AISI [...] Read more.

This experimental study presents the machinability comparison of TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN coated carbide inserts in hard turning AISI 4340 steel. The primary purpose of this research is to determine the most appropriate cutting inserts in turning hardened AISI 4340 (30–40 HRC) steel considering surface roughness (Ra), cutting sound (Cs), power consumption (P), radial force (Fx), tangential force (Fy), and feed force (Fz). To fulfill this objective, the turning experiments for each tool were executed based on the Taguchi L₉ design. The comparative assessment of cutting tools revealed that the TiAlSiN coated tool exhibited superior performance compared to other tools. Machining with the TiCN-Al₂O₃-TiN coated tool showed 32.05% greater roughness than with the TiAlN-TiN coated tool, and 68.80% higher surface roughness than the TiAlSiN coated tool. The main novelty of this research is considering the cutting sound and power consumption as responses to select the most suitable cutting tools. Moreover, a novel grey-crow search hybrid was executed to perceive the optimal value of the input parameters. The optimal local value of cutting speed for the TiAlSiN coated tool was found to be 220 m/min, while for the TiCN-Al₂O₃-TiN and TiAlN-TiN tools, it was the same as 182 m/min. Considering the optimum cutting parameters, the material removal rate for TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN was found to be 639.9 mm³/min, 606.4 mm³/min, and 761.2 mm³/min, respectively. Thus, the TiAlSiN coated tool has greater MRR capability in comparison to other tools. Therefore, this leads to the conclusion that the TiAlSiN tool may be the better choice in comparison to other selected tools for turning hardened steels. Full article

(This article belongs to the Special Issue Advanced Precision Machining of Metallic Surfaces)

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19 pages, 8696 KiB

Open AccessArticle

Study on Friction Characteristics of AA7075 Aluminum Alloy under Pulse Current-Assisted Hot Stamping

by Jiansheng Xia, Rongtao Liu, Jun Zhao, Yingping Guan and Shasha Dou

Metals 2023, 13(5), 972; https://doi.org/10.3390/met13050972 - 17 May 2023

Viewed by 1134

Abstract

Friction during contact between metals can be very complex in pulse current-assisted forming. Based on stamping process characteristics, a reciprocating friction tester was designed to study the friction characteristics between AA7075 aluminum alloy and P20 steel under different current densities. Origin software was [...] Read more.

Friction during contact between metals can be very complex in pulse current-assisted forming. Based on stamping process characteristics, a reciprocating friction tester was designed to study the friction characteristics between AA7075 aluminum alloy and P20 steel under different current densities. Origin software was used to process the experimental data, and a current friction coefficient model was established for the pulse current densities. The results show that the friction coefficient of the aluminum alloy sheet decreased with the increase in the pulse current density (2–10 A/mm²). After that, the friction mechanism was determined by observing microscopic morphology and SEM: some oxide cracked on the friction surface when the current was large. Finally, finite element simulations with Abaqus software and a cylindrical case validated the constant and current friction coefficient models. The thickness distribution patterns of the fixed friction coefficient and the current coefficient model were compared with an actual cylindrical drawing part. The results indicate that the new current friction model had a better fit than the fixed one. The simulation results are consistent with the actual verification results. The maximum thinning was at the corner of the stamping die, which improved the simulation accuracy by 7.31%. This indicates the effectiveness of the pulse current friction model. Full article

(This article belongs to the Special Issue Aluminum Alloys and Aluminum-Based Matrix Composites)

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