Metals

11 pages, 22722 KiB

Open AccessArticle

Correlation between Microstructures and Tensile Properties in Friction Stir Welding Joint of Zn-Modified 5083 Al Alloy

by Zhixiong Zhu, Zongling Lang, Meng Xu, Pan Nie, Xingxu Jiang, Fengfeng Hu and Yongyong Lin

Metals 2022, 12(7), 1234; https://doi.org/10.3390/met12071234 - 21 Jul 2022

Viewed by 1297

Abstract

Various Zn contents were utilized as an alloy element adding in the AA5083 aluminum alloys to optimize the properties. The subsequent characterizing techniques show that the hardness distribution of the friction stir welding (FSW) joint is ‘W’ shaped with the nugget zone relatively [...] Read more.

Various Zn contents were utilized as an alloy element adding in the AA5083 aluminum alloys to optimize the properties. The subsequent characterizing techniques show that the hardness distribution of the friction stir welding (FSW) joint is ‘W’ shaped with the nugget zone relatively high, and the hardness of the thermo-mechanical affected zone (TMAZ) being the lowest. The joint with rotation speed of 600 rpm has the best mechanical properties and no welding defects appear. The grain deformation of the TMAZ is greater under the action of the welding tool and grain growth occurs in the heat affected zone (HAZ). Based on slow strain rate testing (SSRT), the FSW joint of the AA5083 alloy containing Zn 0.50 wt.% showed the highest resistance to stress corrosion cracking (SCC), which is probably due to the formation of Zn phase in place of the β (Al₃Mg₂) phase during welding. Full article

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12 pages, 5293 KiB

Open AccessArticle

Effect of Q235 Hot-Dip Galvanized and Post-Casting T6 Heat Treatment on Microstructure and Mechanical Properties of Interfacial between AZ63 and Q235 by Solid-Liquid Compound Casting

by Jiahong Dai, Hongmei Xie, Yangyang Zhou, Qin Zou, Yuan Tian, Qingshan Yang, Cheng Peng, Bin Jiang and Jianyue Zhang

Metals 2022, 12(7), 1233; https://doi.org/10.3390/met12071233 - 21 Jul 2022

Cited by 4 | Viewed by 1399

Abstract

AZ63 sacrificial anode is widely used to protect buried metal pipelines and reinforced concrete structures and so on. The interfacial metallurgical bonding between AZ63 sacrificial anode and Q235 wiring terminal directly affects its cathodic protection performance. Therefore, microstructure and mechanical properties of interfacial [...] Read more.

AZ63 sacrificial anode is widely used to protect buried metal pipelines and reinforced concrete structures and so on. The interfacial metallurgical bonding between AZ63 sacrificial anode and Q235 wiring terminal directly affects its cathodic protection performance. Therefore, microstructure and mechanical properties of interfacial between AZ63 and Q235 by solid–liquid compound casting with hot-dip galvanized and post-casting solution-aging treatment (T6) were investigated. The results indicate that hot-dip galvanizing on the surface of Q235 is beneficial to the formation of intermetallic compounds at the interface. At the same time, it can promote the metallurgical bonding of the interface between AZ63 and Q235. After T6 heat treatment, the intermetallic compound at the interface between AZ63 and galvanized Q235 was refined. The electron-probe microanalyzer (EPMA) revealed that the intermetallic compounds at the interfaces between AZ63 and galvanized Q235 were Fe₂Al₅ before and after T6 treatment. Push-out testing and microhardness were used to investigate the mechanical properties of interface between AZ63 and Q235. It is shown that the hot-dip galvanization of the Q235 surface and T6 treatment were beneficial to improve the metallurgical bonding shear strength and microhardness of the interface. After T6 heat treatment, the highest shear strength at the interface between AZ63 and galvanized Q235 was up to 31.9 ± 1.9 MPa. Full article

(This article belongs to the Special Issue Magnesium Alloys: Structure, Properties and Applications)

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19 pages, 5147 KiB

Open AccessArticle

Parametric Study and Investigations of Bead Geometries of GMAW-Based Wire–Arc Additive Manufacturing of 316L Stainless Steels

by Rakesh Chaudhari, Heet Parmar, Jay Vora and Vivek K. Patel

Metals 2022, 12(7), 1232; https://doi.org/10.3390/met12071232 - 21 Jul 2022

Cited by 21 | Viewed by 2705

Abstract

Appropriate selection of wire–arc additive manufacturing (WAAM) variables imparts bead geometries with characteristics of multi-layer structures. Thus, the present study aimed to optimize the gas metal arc welding (GMAW)-based WAAM variables of travel speed (TS), wire feed speed (WFS), and voltage (V) for [...] Read more.

Appropriate selection of wire–arc additive manufacturing (WAAM) variables imparts bead geometries with characteristics of multi-layer structures. Thus, the present study aimed to optimize the gas metal arc welding (GMAW)-based WAAM variables of travel speed (TS), wire feed speed (WFS), and voltage (V) for the bead geometries of bead width (BW) and bead height (BH) on an SS 316L substrate. Single-layer depositions were made through a metallic wire of SS 316L by following an experimental matrix of the Box–Behnken design (BBD) technique. Multivariable regression equations were generated for design variables and responses, and ANOVA was used to investigate the feasibility of the obtained regression equations. WFS was the highest contributor affecting the BW, followed by V and TS, while WFS was again the highest contributor affecting the BH, followed by TS and V. Heat transfer search (HTS) optimization was used to attain optimal combinations. The single-objective optimization result showed a maximum bead height and minimum bead width of 6.72 mm and 3.72 mm, respectively. A multi-layer structure was then fabricated by considering an optimization case study, and it showed optimized parameters at a WFS of 5.50 m/min, TS of 141 mm/min, and voltage of 19 V with the bead height and bead width of 5.01 mm and 7.81 mm, respectively. The multi-layered structure obtained at the optimized parameter was found to be free from disbonding, and seamless fusion was detected between the obtained layers of the structure. The authors believe that the present study will be beneficial for industrial applications for the fabrication of multi-layer structures. Full article

(This article belongs to the Special Issue Additive Technologies, Advanced Joining Technology and Study of Weld Joints)

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14 pages, 5502 KiB

Open AccessFeature PaperArticle

Rheological Behavior of Inconel 718 Powder for Electron-Beam Melting

by Laura Cordova, Ahmad Raza and Eduard Hryha

Metals 2022, 12(7), 1231; https://doi.org/10.3390/met12071231 - 21 Jul 2022

Cited by 2 | Viewed by 2254

Abstract

Understanding the impact of powder reuse in powder-bed-fusion electron beams (PBF-EB) is key to maintain the processability and yield. Powder oxidation, due to exposure to high temperatures for a prolonged period of time, can lead to a decrease in electrical conductivity of the [...] Read more.

Understanding the impact of powder reuse in powder-bed-fusion electron beams (PBF-EB) is key to maintain the processability and yield. Powder oxidation, due to exposure to high temperatures for a prolonged period of time, can lead to a decrease in electrical conductivity of the powder and, hence, electrostatic forces that originate during interaction with the electron beam. The effect of oxidation on physical properties as powder rheological properties, apparent/tap density and charging are studied in this work. The analysis using Scanning Electron Microscopy (SEM) shows thermodynamically stable Al-rich oxide particulates (sized 100–200 nm) covering the surface of the reused powder particles, with an increase of 20% in bulk oxygen in comparison to the virgin powder and, measured by X-ray Photoelectron Spectroscopy (XPS), average oxide thickness of circa 13 nm in the reused powder. On the one hand, reusing the powder positively impacted the flowability studied using the Revolution Powder Analyzer (RPA), in which the avalanche angle was decreased from 37 deg to 30 deg, for virgin and reused powder, respectively. The volume fraction of loose powder was similar for both virgin and reused powder, 57% and 56%, respectively, while the packed volume fraction was measured lower in the reused (57%) than the virgin powder (60%). On the other hand, the charging behavior, studied using the ION Charge Module of the powder, worsened; this almost doubled in the reuse powder (−9.18 V/g) compared to the virgin powder (−5.84 V/g). The observation of ejected particles from the build volume is attributed to the charging behavior and lower packing volume fraction in the reused powder. Full article

(This article belongs to the Special Issue Metal Powder for Additive Manufacturing: Manufacturing, Properties and Degradation)

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14 pages, 16063 KiB

Open AccessArticle

Friction and Wear Properties of CoCrFeNiMnSn_x High Entropy Alloy Coatings Prepared via Laser Cladding

by Jie Sun, Sichao Dai, Dabin Zhang, Wudong Si, Benchi Jiang, Da Shu, Lulu Wu, Chao Zhang, Meisong Zhang and Xinyan Xiong

Metals 2022, 12(7), 1230; https://doi.org/10.3390/met12071230 - 21 Jul 2022

Cited by 4 | Viewed by 1846

Abstract

Due to its unique single-phase multivariate alloy characteristics and good low-temperature mechanical properties, CoCrFeNiMn high entropy alloy (HEA) has attracted the interest of many researchers in recent years. In this paper, to improve the wear resistance of Q235 alloy steel surface, CoCrFeNiMnSn_x [...] Read more.

Due to its unique single-phase multivariate alloy characteristics and good low-temperature mechanical properties, CoCrFeNiMn high entropy alloy (HEA) has attracted the interest of many researchers in recent years. In this paper, to improve the wear resistance of Q235 alloy steel surface, CoCrFeNiMnSn_x HEA coatings were prepared on the surface of Q235 steel via laser cladding. X-ray diffractometry, optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectrometry were used to determine the microstructure and chemical composition. The research findings revealed that the CoCrFeNiMn HEA coatings were formed from a single FCC phase. As the Sn content in the coating increased, a new MnNi₂Sn phase formed. Microhardness and friction and wear results showed that when the mole content of Sn was 0.2, the hardness of the CoCrFeNiMn HEA coating was increased by approximately 45%, the friction coefficient decreased by 0.168, and the wear loss decreased by 16.6%. Three-dimensional noncontact morphology and SEM results revealed that the wear mechanisms of CoCrFeNiMn HEA coatings were abrasive wear, delamination wear and a small amount of oxidative wear under dry friction conditions, whereas the friction mechanisms of CoCrFeNiMnSn_0.2 HEA coatings were primarily abrasive wear and oxidative wear. Full article

(This article belongs to the Special Issue Wear and Corrosion Behavior of High-Entropy Alloy)

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14 pages, 4229 KiB

Open AccessArticle

Optimizing Metallographic Etchants for Ancient Gold and Silver Materials

by Shengyu Liu, Zisang Gong, Haizi Lu, Wei Zhang, Yanru Ma, Xiaolin Yang, Zhenda Xie, Gang Hu and Dongbo Hu

Metals 2022, 12(7), 1229; https://doi.org/10.3390/met12071229 - 20 Jul 2022

Cited by 1 | Viewed by 1821

Abstract

In recent years, with the excavation of an increasing amount of gold and silver artifacts, there has been an urgent need to optimize the formulations and methods of metallographic etching. Herein, a kinetic control study is performed to investigate the mechanisms leading to [...] Read more.

In recent years, with the excavation of an increasing amount of gold and silver artifacts, there has been an urgent need to optimize the formulations and methods of metallographic etching. Herein, a kinetic control study is performed to investigate the mechanisms leading to poor results when etching ancient gold materials with aqua regia, i.e., when secondary AgCl impurities form during the etching of the sample surface. To this end, a concentrated ammonia and sodium thiosulfate solution is used to dissolve AgCl impurities and obtain high-quality metallographic images of ancient gold materials using a coordination reaction to generate stable free-state coordination ions from Ag⁺. On this basis, a ferric chloride + sodium thiosulfate method is proposed to optimize the formulation of the etchant for ancient silver materials. The formulation is efficient, safe and easy to handle, and solves the problems of the easy failure of the commonly used etchant of ammonia + hydrogen peroxide and the complicated preparation process of acidified potassium dichromate while maintaining the long-term stability of the etched Ag–Cu alloy samples. Full article

(This article belongs to the Section Structural Integrity of Metals)

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4 pages, 347 KiB

Open AccessEditorial

Casting Alloy Design and Characterization

by Eleani Maria Da Costa and Carlos Alexandre Dos Santos

Metals 2022, 12(7), 1228; https://doi.org/10.3390/met12071228 - 20 Jul 2022

Cited by 1 | Viewed by 1196

Abstract

Metal casting processes routinely used in the foundry industry (e.g., gravity or pressure casting) are subject to a wide range of operational parameters. Since there is a close correlation between solidification conditions, microstructure, and properties, the effects of the solidification thermal parameters and [...] Read more.

Metal casting processes routinely used in the foundry industry (e.g., gravity or pressure casting) are subject to a wide range of operational parameters. Since there is a close correlation between solidification conditions, microstructure, and properties, the effects of the solidification thermal parameters and alloying elements on microstructure designs and the resulting properties in cast alloys have stimulated new research interest. Thus, this Special Issue aims to collect research articles focused on the design and characterization of cast alloys, especially on the interrelationship between solidification, microstructure, and properties; both experimental and theoretical research are welcome for contribution. Full article

(This article belongs to the Special Issue Casting Alloy Design and Characterization)

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30 pages, 5044 KiB

Open AccessReview

A Review on Fabrication of Cylindrical and Rotating Parts by Thermoelectric-Erosion Based Turning Processes

by Sujeet Kumar Chaubey and Kapil Gupta

Metals 2022, 12(7), 1227; https://doi.org/10.3390/met12071227 - 20 Jul 2022

Cited by 2 | Viewed by 1761

Abstract

Nowadays, advanced turning processes are extensively being adopted to perform different types of turning operations such as straight turning, taper turning on Hastelloy, Nimonic, and Inconel, stainless steel, and tool steel to fabricate better quality cylindrical and rotating parts such as miniature-bars, miniature-pins, [...] Read more.

Nowadays, advanced turning processes are extensively being adopted to perform different types of turning operations such as straight turning, taper turning on Hastelloy, Nimonic, and Inconel, stainless steel, and tool steel to fabricate better quality cylindrical and rotating parts such as miniature-bars, miniature-pins, miniature-electrodes, and miniature-tools. This paper presents a review of the previous research conducted on the turning of miniature cylindrical bars using thermoelectric-erosion based turning processes namely thermoelectric-erosion turning (TET) and wire-assisted thermoelectric-erosion turning (WTET). It also highlights work and tool electrode materials, types of dielectrics, detailed specifications of turning, types of turning, process parameters, performance measures, advantages and limitations, and key findings. The paper ends with conclusions and future research directions. This paper aims to facilitate researchers and scholars by highlighting the potential and capabilities of TET and WTET processes and providing relevant information for ease of fabrication of miniature parts and components from a wide range of difficult-to-machine materials. Full article

(This article belongs to the Special Issue Machining and Finishing Processes for Metals)

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13 pages, 6859 KiB

Open AccessArticle

The Influence of Laser Power and Scan Speed on the Dimensional Accuracy of Ti6Al4V Thin-Walled Parts Manufactured by Selective Laser Melting

by Georgina Miranda, Susana Faria, Flávio Bartolomeu, Elodie Pinto, Nuno Alves and Filipe Samuel Silva

Metals 2022, 12(7), 1226; https://doi.org/10.3390/met12071226 - 20 Jul 2022

Cited by 4 | Viewed by 1745

Abstract

Laser Powder Bed Fusion (LPBF) technologies such as Selective Laser Melting (SLM) are being increasingly considered as viable production routes. This paradigm change demands an in-depth understanding of the fabrication process and variables, as previous studies have shown that energy density calculation alone [...] Read more.

Laser Powder Bed Fusion (LPBF) technologies such as Selective Laser Melting (SLM) are being increasingly considered as viable production routes. This paradigm change demands an in-depth understanding of the fabrication process and variables, as previous studies have shown that energy density calculation alone is insufficient, because parts fabricated using similar energy density, but using different combinations of parameters, can display significantly different properties and dimensions. Thin-walled parts are particularly influenced by processing parameters; in this sense, this study explores the influence of laser power and scan speed on the dimensions of Ti6Al4V thin-walled tubes. Predictive models for manufacturing Ti6Al4V thin-walled tubes were developed using Response Surface Methodology (RSM), and the most influential (single and combined) factors were determined using Analysis of Variance (ANOVA). Three models were obtained: for the wall melt zone thickness, the total wall thickness, and the hole width. Full article

(This article belongs to the Special Issue Selective Laser Melting: Advantages and Challenges)

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15 pages, 7613 KiB

Open AccessArticle

Effects of Metal and Fluoride Powders Deposition on Hot-Cracking Susceptibility of 316L Stainless Steel in TIG Welding

by Kamel Touileb, Abousoufiane Ouis, Abdeljlil Chihaoui Hedhibi, Albaijan Ibrahim and Hany S. Abdo

Metals 2022, 12(7), 1225; https://doi.org/10.3390/met12071225 - 20 Jul 2022

Cited by 1 | Viewed by 1444

Abstract

This study aims to investigate the effects on the hot cracking susceptibility of fluoride powders such as CaF₂, NaF, LiF, and metal powders such as Mn, Ti, Nb and mixed Ti-Nb deposited on the 316L stainless steel during the TIG (Tungsten [...] Read more.

This study aims to investigate the effects on the hot cracking susceptibility of fluoride powders such as CaF₂, NaF, LiF, and metal powders such as Mn, Ti, Nb and mixed Ti-Nb deposited on the 316L stainless steel during the TIG (Tungsten Inert Gas) welding process. A self-restraint hot cracking bench test using specimens of trapezoidal shape and 3 mm of thickness was selected. The obtained results of the weldability with the different powders were compared with those obtained with the conventional TIG parent-metal weld. The susceptibility to hot cracking was evaluated by the length of the crack and by the critical width at the end of the crack propagation. The formed cracks were first revealed by the liquid penetrant test, and then the surfaces of cracks were observed and analyzed by SEM-EDS-XRD tools. Among the powders tested, single Nb powder and the mixed flux of 80% Nb + 20% Ti exhibited the lowest crack length. The crack propagation ended at 22 mm of length and 30.8 mm of width. The analyses of the fracture surfaces of cracks revealed the presence of Niobium carbide (Nb₂C), titanium, chromium, niobium oxide (TiO_0.6Cr_0.2Nb_0.0202) complex compounds and cementite (Fe₃C) at the interdendritic zones. Full article

(This article belongs to the Section Welding and Joining)

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12 pages, 2822 KiB

Open AccessArticle

Effects of Deep Rolling on the Microstructure Modification and Fatigue Life of 35Cr2Ni4MoA Bolt Threads

by Xianmo Wang, Xiyao Xiong, Kanghua Huang, Shaojun Ying, Mingjun Tang, Xinhe Qu, Wen Ji, Chengkai Qian and Zhipeng Cai

Metals 2022, 12(7), 1224; https://doi.org/10.3390/met12071224 - 20 Jul 2022

Cited by 6 | Viewed by 2024

Abstract

Stress concentration on a bolt thread, resulting from its own special shape, poses a threat to the fatigue strength of the bolt, which directly affects the safety and reliability of aircraft. In this paper, deep rolling was applied to a bolt thread to [...] Read more.

Stress concentration on a bolt thread, resulting from its own special shape, poses a threat to the fatigue strength of the bolt, which directly affects the safety and reliability of aircraft. In this paper, deep rolling was applied to a bolt thread to improve its fatigue resistance. The properties of the plastic deformation layer, including the surface morphology, microstructure, hardness, and residual stress, as well as the fatigue life of the bolt, were characterized by means of SEM, white light interferometer, EBSD, and fatigue tests. The results showed that the surface roughness of the bottom of the thread was reduced to 0.255 μm, and a plastic deformation layer of about 300 μm in depth was formed after rolling. A more compact streamlined fibrous microstructure, composed of refined grains, with increased dislocation density and hardness and decreased tensile residual stress, was formed in the plastic deformation layer. The fatigue life of the bolts after rolling increased by about 113%, evidencing the comprehensive result of these microstructure modifications. Full article

(This article belongs to the Topic Surface Treatments for Protecting from Fracture and Fatigue Damage)

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14 pages, 4786 KiB

Open AccessArticle

Selective Laser Melting of Free-Assembled Stainless Steel 316L Hinges: Optimization of Volumetric Laser Energy Density and Joint Clearance

by Cho-Pei Jiang, Alvian Toto Wibisono, Shun-Hsien Wang, Tim Pasang and Maziar Ramezani

Metals 2022, 12(7), 1223; https://doi.org/10.3390/met12071223 - 20 Jul 2022

Cited by 3 | Viewed by 1913

Abstract

Selective laser melting technology is one of the metal additive manufacturing technologies that can convert metal powder to complex parts without the assembly process. This study aims to optimize the volumetric laser energy density for printing 3D metal objects with hinges geometry. The [...] Read more.

Selective laser melting technology is one of the metal additive manufacturing technologies that can convert metal powder to complex parts without the assembly process. This study aims to optimize the volumetric laser energy density for printing 3D metal objects with hinges geometry. The material is stainless steel 316L powder. The volumetric laser energy densities ranging from 4.1 J/mm³ to 119.1 J/mm³ are applied to fabricate 3D free-assembled hinges with various clearances of 0.38 mm, 0.39 mm, 0.40 mm, and 0.41 mm and investigate the relationship between volumetric laser energy density and clearance. A multibody model, consisting of nine segments with eight hinges, is proposed to be printed with the optimized volumetric laser energy density. The optical microscope and the hardness test are performed to observe the porosity and hardness property of the SLMed object. The result shows that laser energy densities between 105.5 J/mm³ and 119.1 J/mm³ can produce the high densification of SLMed objects with a porosity defect of 0.24% to 0.20% and hardness in the range of 207 HV to 215 HV. The optimization of laser energy densities is in the range of 105.5 J/mm³ to 119.1 J/mm³, which can be used to fabricate the movable hinges with a minimum clearance size of 0.41 mm. The proposed dinosaur object is printed successfully and all joints are rotatable. Full article

(This article belongs to the Section Additive Manufacturing)

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14 pages, 4207 KiB

Open AccessArticle

Influence of Plastic Strain Control on Martensite Evolution and Fatigue Life of Metastable Austenitic Stainless Steel

by Matthias Droste, Sebastian Henkel, Horst Biermann and Anja Weidner

Metals 2022, 12(7), 1222; https://doi.org/10.3390/met12071222 - 19 Jul 2022

Cited by 2 | Viewed by 1420

Abstract

Metastable austenitic stainless steel was investigated during fatigue tests under strain control with either constant total or constant plastic strain amplitude. Two different material conditions with coarse-grained and ultrafine-grained microstructure were in focus. The influence of plastic strain control of the fatigue test [...] Read more.

Metastable austenitic stainless steel was investigated during fatigue tests under strain control with either constant total or constant plastic strain amplitude. Two different material conditions with coarse-grained and ultrafine-grained microstructure were in focus. The influence of plastic strain control of the fatigue test on both the martensitic phase transformation as well as on the fatigue lives is discussed. In addition, an approach for calculating the Coffin–Manson–Basquin parameters to estimate fatigue lives based on strain-controlled tests at constant total strain amplitudes is proposed for materials undergoing a strong secondary hardening due to martensitic phase transformation. Full article

(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)

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13 pages, 25785 KiB

Open AccessArticle

In-Production Rheometry of Semi-Solid Metal Slurries

by Anders E. W. Jarfors, Mahdi Jafari, Muhammed Aqeel, Patrik Liljeqvist and Per Jansson

Metals 2022, 12(7), 1221; https://doi.org/10.3390/met12071221 - 19 Jul 2022

Cited by 4 | Viewed by 1697

Abstract

Semi-solid aluminium alloy processing (SSM) has advanced into a more mature process with many applications. The current paper aims to investigate the in-process behaviour of a production slurry using an engineering approach to estimate the properties. A method to assess the rheological properties [...] Read more.

Semi-solid aluminium alloy processing (SSM) has advanced into a more mature process with many applications. The current paper aims to investigate the in-process behaviour of a production slurry using an engineering approach to estimate the properties. A method to assess the rheological properties of a semi-solid metal slurry was tested and found capable of producing meaningful measurements. The foundations of this were to use a Rushton turbine setup for the assessment through a model to optimize the factors included in the slurry rheology. In the analysis of the static and dynamic part of the viscosity, it was concluded that the slurry turns increasingly into a solid with increasing solid fractions where the static shear strength dominates the rheology more and more compared to the dynamic components. The static yield strength was also found significantly more dominant with increasing solid fraction, suggesting that the industrial-scale analysis using models based on Ostwald–de Waale and Carreau modelling is far from sufficient for a process, such as the RheoMetal process, with a very rapid slurry generation. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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15 pages, 4480 KiB

Open AccessArticle

Phase-Field Simulation of Spinodal Decomposition in Mn-Cu Alloys

by Darío A. Sigala-García, Víctor M. López-Hirata, Maribel L. Saucedo-Muñoz, Héctor J. Dorantes-Rosales and José D. Villegas-Cárdenas

Metals 2022, 12(7), 1220; https://doi.org/10.3390/met12071220 - 19 Jul 2022

Cited by 2 | Viewed by 2784

Abstract

The spinodal decomposition was studied in the aged Mn-40 at. %Cu, Mn-30 at. %Cu, Mn-20 at. %Cu alloys using a phase-field model based on the Cahn–Hillard equation, considering a subregular solution model and the energy contribution of the magnetic behavior. The simulations were [...] Read more.

The spinodal decomposition was studied in the aged Mn-40 at. %Cu, Mn-30 at. %Cu, Mn-20 at. %Cu alloys using a phase-field model based on the Cahn–Hillard equation, considering a subregular solution model and the energy contribution of the magnetic behavior. The simulations were performed at aging temperatures of 300, 400, and 500 °C for times from 1 to 240 min. The growth kinetics of the Mn concentration profiles with time indicated clearly that the phase decomposition of the supersaturated solid solution γ into a mixture of Mn-rich γ′ and Cu-rich γ phases occurred by the spinodal decomposition mechanism. Moreover, the phase decomposition at the early stages of aging exhibited the characteristic morphology of spinodal decomposition, an interconnected and percolated microstructure of the decomposed phases. The most rapid growth kinetics of spinodal decomposition occurred for the aging of Mn-20 and 30 at. %Cu alloys because of the higher driving force. The presence of the phase decomposition is responsible for the increase in hardness, as well as the improvement of the damping capacity of Mn-Cu alloys. Full article

(This article belongs to the Special Issue Computer Methods in Metallic Materials)

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10 pages, 3875 KiB

Open AccessFeature PaperArticle

Effect of Cooling Mode on the Microstructure of High-Strength Steel during Hot Rolling

by Hongliang Liu, Wenbin Du, Hongzhou Lu, Yujing Fu, Shuai Yu and Chengjun Liu

Metals 2022, 12(7), 1219; https://doi.org/10.3390/met12071219 - 19 Jul 2022

Cited by 2 | Viewed by 1522

Abstract

This paper studies the effect of extreme cooling and traditional cooling on the microstructure of high-strength steel during hot rolling by adjusting the cooling process, combining the theoretical calculation and the thermal simulation experiment, and using metallographic microscope, scanning electron microscope (SEM), and [...] Read more.

This paper studies the effect of extreme cooling and traditional cooling on the microstructure of high-strength steel during hot rolling by adjusting the cooling process, combining the theoretical calculation and the thermal simulation experiment, and using metallographic microscope, scanning electron microscope (SEM), and electron backscattered diffraction (EBSD) analysis methods in order to solve the problem of coil collapse in the production process of high-strength steel. The research results show that compared with the traditional cooling method, the front-section fast cooling mode can rapidly cool the hot-rolled sheet to the “nose tip” temperature of the ferrite transformation of the time-temperature-phase-transition (TTT) curve, which can promote the transformation of the material to ferrite, increase the proportion of ferrite, and make the grain size of the organization finer. It helps to improve the overall mechanical properties of the material and reduce coil collapse defects. The front-section fast cooling mode achieves good results in industrial application, the proportion of coil collapse reduces from 9.363% to 0.533%, and the problem of coil collapse is significantly improved. Full article

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14 pages, 11230 KiB

Open AccessArticle

Effect of Microstructure on Mechanical Properties of 2519A Aluminum Alloy in Thickness Direction

by Qiang Hu, Wenhui Liu, Changping Tang, Chenbing Zhao, Mingyue Xiao and Yufeng Song

Metals 2022, 12(7), 1218; https://doi.org/10.3390/met12071218 - 19 Jul 2022

Cited by 2 | Viewed by 1234

Abstract

2519A aluminum alloy thick plate is a promising structural material in the field of military industries, owing to its low density, high tensile strength and excellent ballistic performance. However, the nonuniformly distributed microstructure along the thickness direction of this alloy leads to delamination [...] Read more.

2519A aluminum alloy thick plate is a promising structural material in the field of military industries, owing to its low density, high tensile strength and excellent ballistic performance. However, the nonuniformly distributed microstructure along the thickness direction of this alloy leads to delamination cracks, which restrict its further application in light armor fields. In order to understand the mechanism of delamination cracking along the thickness direction, the effect of the microstructure on the mechanical properties of 2519A aluminum alloy in the thickness direction was investigated. The results show that the elongation and critical stress intensity factor values (ΔK_cr) of the alloy in the thickness direction are 45.8% and 44.1% lower than the values in the rolling direction, respectively. The low mechanical properties of the alloy may be due to the short distance between the second phase, the weak binding force of grain boundaries and the disharmonious deformation caused by the inhomogeneous distribution of the microstructure. This study provides a basis for improving the mechanical properties and delamination cracking of the alloy along the thickness direction. Full article

(This article belongs to the Special Issue Microstructural Evolution and Mechanical Properties of Aluminum Alloys)

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15 pages, 3991 KiB

Open AccessArticle

In Situ X-ray Radiography and Computational Modeling to Predict Grain Morphology in β-Titanium during Simulated Additive Manufacturing

by Chris Jasien, Alec Saville, Chandler Gus Becker, Jonah Klemm-Toole, Kamel Fezzaa, Tao Sun, Tresa Pollock and Amy J. Clarke

Metals 2022, 12(7), 1217; https://doi.org/10.3390/met12071217 - 19 Jul 2022

Cited by 3 | Viewed by 1920

Abstract

The continued development of metal additive manufacturing (AM) has expanded the engineering metallic alloys for which these processes may be applied, including beta-titanium alloys with desirable strength-to-density ratios. To understand the response of beta-titanium alloys to AM processing, solidification and microstructure evolution needs [...] Read more.

The continued development of metal additive manufacturing (AM) has expanded the engineering metallic alloys for which these processes may be applied, including beta-titanium alloys with desirable strength-to-density ratios. To understand the response of beta-titanium alloys to AM processing, solidification and microstructure evolution needs to be investigated. In particular, thermal gradients (Gs) and solidification velocities (Vs) experienced during AM are needed to link processing to microstructure development, including the columnar-to-equiaxed transition (CET). In this work, in situ synchrotron X-ray radiography of the beta-titanium alloy Ti-10V-2Fe-3Al (wt.%) (Ti-1023) during simulated laser-powder bed fusion (L-PBF) was performed at the Advanced Photon Source at Argonne National Laboratory, allowing for direct determination of Vs. Two different computational modeling tools, SYSWELD and FLOW-3D, were utilized to investigate the solidification conditions of spot and raster melt scenarios. The predicted Vs obtained from both pieces of computational software exhibited good agreement with those obtained from in situ synchrotron X-ray radiography measurements. The model that accounted for fluid flow also showed the ability to predict trends unobservable in the in situ synchrotron X-ray radiography, but are known to occur during rapid solidification. A CET model for Ti-1023 was also developed using the Kurz–Giovanola–Trivedi model, which allowed modeled Gs and Vs to be compared in the context of predicted grain morphologies. Both pieces of software were in agreement for morphology predictions of spot-melts, but drastically differed for raster predictions. The discrepancy is attributable to the difference in accounting for fluid flow, resulting in magnitude-different values of Gs for similar Vs. Full article

(This article belongs to the Special Issue Numerical Simulation of Solidification Processes)

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5 pages, 205 KiB

Open AccessEditorial

Advances in Anti-Corrosion Polymeric and Paint Coatings on Metals: Preparation, Adhesion, Characterization and Application

by Maxim A. Petrunin

Metals 2022, 12(7), 1216; https://doi.org/10.3390/met12071216 - 19 Jul 2022

Cited by 2 | Viewed by 1558

Abstract

Metals currently remain the main structural material used by various industries for many centuries [...] Full article

(This article belongs to the Special Issue Advances in Anti-corrosion Polymeric and Paint Coatings on Metals: Preparation, Adhesion, Characterization and Application)

12 pages, 7419 KiB

Open AccessArticle

Study on the Effects of Multiple Laser Shock Peening Treatments on the Electrochemical Corrosion Performance of Welded 316L Stainless Steel Joints

by Yuqin Li, Jinyu Fan, Jianzhong Wen, Xiangfan Nie and Liucheng Zhou

Metals 2022, 12(7), 1215; https://doi.org/10.3390/met12071215 - 19 Jul 2022

Cited by 8 | Viewed by 1574

Abstract

To study the influence of laser shock peening on the electrochemical corrosion resistance of welded 316L stainless steel joints, welded 316L stainless steel joints are treated with different laser shock peening treatments (i.e., one, two, and three times). Our analysis employs electron backscattering [...] Read more.

To study the influence of laser shock peening on the electrochemical corrosion resistance of welded 316L stainless steel joints, welded 316L stainless steel joints are treated with different laser shock peening treatments (i.e., one, two, and three times). Our analysis employs electron backscattering diffraction (EBSD), scanning electron microscopy (SEM), X-ray diffraction (XRD), an X-ray stress meter, and electrochemical corrosion tests to observe and analyze the microstructure, structural composition, residual stress, and corrosion resistance in different areas of the surface of 316L before and after the laser shock peening. The results show that the residual stress distribution of the welded joints is optimized after laser shock peening, with a maximum residual compressive stress near the matrix of 171 MPa. When the number of laser shock peening treatments is two, the corrosion current reaches a minimum of 9.684×10⁻⁷ A/cm², and optimal pitting resistance is obtained. However, when the number of laser shock peening treatments is further increased to three, the corrosion current increase and the pitting resistance decreases. In summary, the electrochemical corrosion resistance of the welded joints effectively improves after laser shock peening, but its performance begins to decline after three repeated shocks, which is related to the combined effects of stress change and microstructure phase transformation. Full article

(This article belongs to the Special Issue Investigations on Mechanical Properties and Corrosion Resistance of Alloys and Compounds)

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23 pages, 11075 KiB

Open AccessArticle

Thermal Preprocessing of Rapidly Solidified Al 6061 Feedstock for Tunable Cold Spray Additive Manufacturing

by Baillie Haddad, Bryer C. Sousa, Kyle Tsaknopoulos, Victor K. Champagne, Jr., Richard D. Sisson, Jr., Aaron Nardi and Danielle L. Cote

Metals 2022, 12(7), 1214; https://doi.org/10.3390/met12071214 - 18 Jul 2022

Cited by 1 | Viewed by 1714

Abstract

In this work, the influence of thermal pre-processing upon the microstructure and hardness of Al 6061 feedstock powder is considered through the lens of cold spray processing and additive manufacturing. Since solid-state cold spray processes refine and retain microstructural constituents following impact-driven and [...] Read more.

In this work, the influence of thermal pre-processing upon the microstructure and hardness of Al 6061 feedstock powder is considered through the lens of cold spray processing and additive manufacturing. Since solid-state cold spray processes refine and retain microstructural constituents following impact-driven and high-strain rate severe plastic deformation and bonding, thermal pre-processing enables application-driven tuning of the resultant consolidation achieved via microstructural and, therefore, mechanical manipulation of the feedstock prior to use. Microstructural analysis was achieved via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, energy dispersive spectroscopy, and differential thermal calorimetry. On the other hand, nanoindentation testing and analysis were relied upon to quantify pre-processing effects and microstructural evolution influences on the resultant hardness as a function of time at 540 °C. In the case of the as-atomized powder, β-Mg₂Si-, Al-Fe-, and Mg-Si-type phases were observed along polycrystalline grain boundaries. Furthermore, after a 60 min hold time at 540 °C, Al-Fe-Si-Cr-Mn- and Mg-Si-type intermetallic phases were also observed along grain boundaries. Furthermore, the as-atomized hardness at 250 nm of indentation depth was 1.26 GPa and continuously decreased as a function of hold time until reaching 0.88 GPa after 240 min at 540 °C. Finally, contextualization of the observations with tuning cold spray additive manufacturing part performance via powder pre-processing is presented for through-process and application-minded design. Full article

(This article belongs to the Special Issue Modern Cold Spray Technique—2022)

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20 pages, 23599 KiB

Open AccessArticle

A Study on the Development of an Optimization Algorithm and Determination Procedure for Toughness Deterioration Characteristics through Flux Core Arc Heat Input Control of ASTM A553-1 (9% Nickel Steel)

by Minho Park, Jaewoong Kim and Changmin Pyo

Metals 2022, 12(7), 1213; https://doi.org/10.3390/met12071213 - 18 Jul 2022

Cited by 1 | Viewed by 1324

Abstract

The International Maritime Organization has adopted the reduction of carbon dioxide emissions from ships as an important priority, and is continuously strengthening its regulations on marine air pollution. By 2035, it is expected that LNG-powered ships will account for more than 50% of [...] Read more.

The International Maritime Organization has adopted the reduction of carbon dioxide emissions from ships as an important priority, and is continuously strengthening its regulations on marine air pollution. By 2035, it is expected that LNG-powered ships will account for more than 50% of the available ships. Accordingly, the demand for equipment related to LNG-fueled ships is expected to grow as well, requiring the development of a lot of equipment. However, the characteristics of LNG-powered ships mean that they require a high level of reliability and long history of operating reliably. Even when a product is developed, numerous demonstrations and quality assurance measures are needed to reach the technological level ship owners and customers require. Therefore, an optimization procedure to determine the welding quality for 9% Ni steel is necessary. In this study, the heat input criteria that induce brittle fracture characteristics were analyzed to optimize the flux core arc welding process for 9% Ni steel used in the manufacture of LNG storage tanks. We developed an optimization algorithm (Welding Current, Arc Voltage, Welding Speed) that can select a group of fracture conditions by examining the tendency of the tissue to brittle fracture due to excessive heat input among potential quality issues of cryogenic steel. Capable of selecting the range in which quality deterioration occurs, determining quality of a weld and avoiding the range in which toughness degradation occurs, through which a process to derive high quality 9% Ni welds is proposed. Full article

(This article belongs to the Special Issue Welding Metallurgy)

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2 pages, 151 KiB

Open AccessEditorial

Modelling, Test and Practice of Steel Structures

by Zhihua Chen, Hanbin Ge and Siulai Chan

Metals 2022, 12(7), 1212; https://doi.org/10.3390/met12071212 - 18 Jul 2022

Cited by 3 | Viewed by 1446

Abstract

Steel structures have been widely used in civil engineering in recent decades across applications such as large spatial structures, high-rise buildings, and bridges [...] Full article

(This article belongs to the Special Issue Modelling, Test and Practice of Steel Structures)

13 pages, 3625 KiB

Open AccessArticle

Effect of Cold Rolling Prior to Annealing on the Grain Size-Energy Losses Relationship in a Low Carbon Grain Non-Oriented Semi-Processed Electrical Steel

by Nancy Margarita López-Granados, Emmanuel José Gutiérrez-Castañeda and Armando Salinas-Rodríguez

Metals 2022, 12(7), 1211; https://doi.org/10.3390/met12071211 - 17 Jul 2022

Viewed by 2625

Abstract

In this work, the effect of cold deformation prior to annealing treatment on the microstructure and magnetic hysteresis energy losses in a low carbon grain non-oriented semi-processed electrical steel with 0.60 mm thickness was investigated. The samples were subjected to different percentages of [...] Read more.

In this work, the effect of cold deformation prior to annealing treatment on the microstructure and magnetic hysteresis energy losses in a low carbon grain non-oriented semi-processed electrical steel with 0.60 mm thickness was investigated. The samples were subjected to different percentages of deformation, in a range of 5–20% reduction and annealed at temperatures between 650 and 950 °C for 60 min, these were characterized by Optical Microscopy. Meanwhile the energy losses were calculated from the magnetic hysteresis loops using a Vibrating Sample Magnetometer. The experimental results showed that cold deformation increases energy losses by 50% when the steel is deformed 20%, due to microstructural defects that are introduced to the material during deformation. The presence of the microstructural defects was verified through measurements of Full Width at Half Maximum by means of X-ray diffraction. On the other hand, it was observed that annealing at temperatures below

A c_{1}

causes only small changes in the microstructure of the steel, however, it promotes the recovery of magnetic properties by 50% with respect to the deformed material. In contrast, when the material is annealed between

A c_{1}

and

A c_{3} (α + γ

) magnetic properties are recovered ~33% with respect to the initial state and, at values higher than 65% compared to the state of greatest deformation (20%), as a result of both microstructural modification and the evolution of the grain size experienced by the material. Full article

(This article belongs to the Special Issue Advances on the Metallurgy of Electrical Steels)

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11 pages, 6444 KiB

Open AccessArticle

Effect of HIP Defects on the Mechanical Properties of Additive Manufactured Ti6Al4V Alloy

by Ohad Dolev, Tomer Ron, Eli Aghion and Amnon Shirizly

Metals 2022, 12(7), 1210; https://doi.org/10.3390/met12071210 - 17 Jul 2022

Cited by 4 | Viewed by 1756

Abstract

The expanding use of Additive Manufacturing (AM) technology enables engineers and designers to plan and manufacture highly complex geometries that are impossible to manufacture with any other conventional technology. When comparing this with building parts using powder bed technology, the main differences found [...] Read more.

The expanding use of Additive Manufacturing (AM) technology enables engineers and designers to plan and manufacture highly complex geometries that are impossible to manufacture with any other conventional technology. When comparing this with building parts using powder bed technology, the main differences found in the quality of the products concern fracture toughness, fatigue, and inferiority in tensile tests. To overcome these issues, the Hot Isostatic Press (HIP) procedure may be used to improve the material quality by reducing product porosity. Regarding fatigue, the standard procedure consists of HIP and the machining of specimens to their final geometry. However, in many AM parts, geometrical complexity does not enable complementary machining. Recently, some AM vendors integrated in-process milling capabilities into their machines, in an attempt to address this challenge. In this study, the authors examine the effect of the HIP procedure on representative samples in order to demonstrate its effect on the final products of TI-6Al-4V parts. The results indicate that the fatigue limit of HIPed parts can increase by 12%; however, a dramatic decrease in the fatigue limit was observed if any failure in the HIP process occurred. The authors suggest an optional procedure to improve performance in such cases. Full article

(This article belongs to the Section Additive Manufacturing)

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17 pages, 3578 KiB

Open AccessArticle

Theoretical Analysis of Grinding Wheel Deflection Angle on Peripheral Grinding Parameters and Grinding Force

by Changhao Chen, Bin Chen, Chaoqun Wu, Xinghua Gu, Xuehai Liu and Feng Guo

Metals 2022, 12(7), 1209; https://doi.org/10.3390/met12071209 - 17 Jul 2022

Viewed by 1473

Abstract

The peripheral surface of the grinding wheel can grind the rail according to the envelope of the contour of the rail surface, thus a fuller and smoother rail surface can be obtained. Specifically, a better grinding effect can be obtained in that the [...] Read more.

The peripheral surface of the grinding wheel can grind the rail according to the envelope of the contour of the rail surface, thus a fuller and smoother rail surface can be obtained. Specifically, a better grinding effect can be obtained in that the end face of the grinding wheel deviates from the longitudinal section of the rail at a certain angle. Based on the traditional grinding technology theory, the mathematical models of the peripheral grinding parameters (kinematic contact arc length, wheel-rail grinding contact area, and maximum undeformed chip thickness) and the grinding force are established, in which the angle exists between the grinding wheel end face and the rail longitudinal section. The main influence of grinding wheel circumferential speed, grinding wheel kinematic speed, and the deflection angle of the grinding wheel end face on the grinding parameters and the force are analyzed. The result shows that: when there is angle θ in the models, the ratios of peripheral grinding parameters between up-grinding and down-grinding varies monotonically with the increase in v_m, and their maximum variation range is about 12%, v_s has the greatest influence on the peripheral grinding parameters, and the maximum variation range of the ratios is about 20% when the v_s is 10 m/s. With the increase in the grinding width, Fa’ cannot be ignored and will increase gradually with the increase in angle θ. The analysis and conclusion have guiding significance for the structural design, grinding control strategy, and experimental research regarding rail curved surface grinding equipment. Full article

(This article belongs to the Special Issue Advances in Machining Processes of Metallic Materials)

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13 pages, 2751 KiB

Open AccessArticle

Pre-Aging Effect on the Formation of Ω Phase and Mechanical Properties of the Al-Cu-Mg-Ag Alloy

by Puyou Ying, Changhong Lin, Zhiyi Liu, Song Bai, Vladimir Levchenko, Ping Zhang, Jianbo Wu, Tao Yang, Min Huang, Gang Yang, Meng Liu and Mengjia Li

Metals 2022, 12(7), 1208; https://doi.org/10.3390/met12071208 - 16 Jul 2022

Cited by 4 | Viewed by 1489

Abstract

In the present work, different aging treatments were performed to investigate the pre-aging effect on the formation of Ω phase and mechanical properties in Al-Cu-Mg-Ag alloy. The results showed that pre-strain could inhibit the formation of Ω phases, which was detrimental to the [...] Read more.

In the present work, different aging treatments were performed to investigate the pre-aging effect on the formation of Ω phase and mechanical properties in Al-Cu-Mg-Ag alloy. The results showed that pre-strain could inhibit the formation of Ω phases, which was detrimental to the alloy strength. Due to the introduction of pre-aging treatment before pre-strain, the adverse effect of pre-strain on the precipitation of the Ω phase was reduced, and the alloy strength was increased by at least 15 MPa. Besides this, increasing the pre-aging temperature promoted the precipitation of Ω phases, inhibited the formation of θ′ phases, and improved the alloy strength. This was because the higher pre-aging temperature promoted more pre-precipitated Ω phases in the pre-aging process, and most of the pre-precipitated Ω phases could be retained and grew in the subsequent aging process. As a result, the tensile strength of the alloy increased from 523 MPa to 540 MPa. In addition, pre-aging with a higher temperature consumed more solute atoms, leading to less residual solute atoms in the matrix. Thus, the adverse effects of pre-strain, which inhibit the formation of clusters by the segregation of solute atoms, were reduced. Full article

(This article belongs to the Special Issue Microstructural Evolution and Mechanical Properties of Aluminum Alloys)

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16 pages, 2014 KiB

Open AccessFeature PaperArticle

State Parameter-Based Yield Strength Model for Integration in Finite Element User-Material Routines

by Bernhard Viernstein, Tomasz Wojcik and Ernst Kozeschnik

Metals 2022, 12(7), 1207; https://doi.org/10.3390/met12071207 - 15 Jul 2022

Cited by 1 | Viewed by 1216

Abstract

A new state parameter-based user-subroutine for finite-element software packages, which can be used to simulate microstructure-dependent stress–strain relations, is presented. Well-established precipitation kinetics, strain hardening and strengthening models are brought into a condensed form to optimise computational efficiency, without losing their predictive capabilities. [...] Read more.

A new state parameter-based user-subroutine for finite-element software packages, which can be used to simulate microstructure-dependent stress–strain relations, is presented. Well-established precipitation kinetics, strain hardening and strengthening models are brought into a condensed form to optimise computational efficiency, without losing their predictive capabilities. The framework includes main strengthening mechanisms, such as, precipitation strengthening, solid solution strengthening, the cross-core diffusion effect and work hardening. With the novel user-subroutine, the microstructure evolution of various thermo-mechanical treatments on the full integration point grid of the finite element (FE) mesh can be calculated. The validation of the simulations is carried out by mechanical testing as well as microstructure characterisation of an Al-6082 alloy, including transmission electron microscopy (TEM) investigations after various annealing times at 180 °C. Full article

(This article belongs to the Special Issue Finite Element Analysis of Mechanical Behavior of Metallic Materials)

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14 pages, 3641 KiB

Open AccessArticle

Investigations into NO_x Formation Characteristics during Pulverized Coal Combustion Catalyzed by Iron Ore in the Sintering Process

by Junying Wan, Tiejun Chen, Xianlin Zhou, Jiawen Liu, Benjing Shi, Zhaocai Wang and Lanlan Li

Metals 2022, 12(7), 1206; https://doi.org/10.3390/met12071206 - 15 Jul 2022

Cited by 1 | Viewed by 1141

Abstract

Sintering accounts for about 50% of the total NO_x emissions of the iron and steel industry. NO_x emissions from the sintering process can be simulated using the emissions from coke combustion. However, the generation and emission law for NO_x burning [...] Read more.

Sintering accounts for about 50% of the total NO_x emissions of the iron and steel industry. NO_x emissions from the sintering process can be simulated using the emissions from coke combustion. However, the generation and emission law for NO_x burning in the sintering process of pulverized coal is still not clear. The formation characteristics of NO_x during coal combustion catalyzed by iron ore fines and several iron-containing pure minerals were studied in this paper. The results showed that iron ore fines can improve the NO_x emission rate and increase the total NO_x emissions during coal combustion. The type and composition of the iron ore fines have an important impact on the generation and emission of NO_x in the process of coal combustion. The peak concentration and emissions of NO_x in coal combustion flue gas with limonite, hematite or specularite added increased significantly. The peak value for the NO_x concentration in the coal combustion flue gas with magnetite or siderite added increased, but the emissions decreased. Therefore, the generation of NO_x in the sintering process can to a certain extent be controlled by adjusting the type of iron-containing raw materials and the distribution of the iron-containing raw materials and coal. Full article

(This article belongs to the Special Issue Iron Ore Agglomeration)

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26 pages, 4641 KiB

Open AccessFeature PaperArticle

Build-Up an Economical Tool for Machining Operations Cost Estimation

by Francisco J. G. Silva, Vitor F. C. Sousa, Arnaldo G. Pinto, Luís P. Ferreira and Teresa Pereira

Metals 2022, 12(7), 1205; https://doi.org/10.3390/met12071205 - 15 Jul 2022

Cited by 4 | Viewed by 1914

Abstract

Currently, there is a lack of affordable and simple tools for the estimation of these costs, especially for machining operations. This is particularly true for manufacturing SMEs, in which the cost estimation of machined parts is usually performed based only on required material [...] Read more.

Currently, there is a lack of affordable and simple tools for the estimation of these costs, especially for machining operations. This is particularly true for manufacturing SMEs, in which the cost estimation of machined parts is usually performed based only on required material for part production, or involves a time-consuming, non-standardized technical analysis. Therefore, a cost estimation tool was developed, based on the calculated machining times and amount of required material, based on the final drawing of the requested workpiece. The tool was developed primarily for milling machines, considering milling, drilling, and boring/threading operations. Regarding the considered materials, these were primarily aluminum alloys. However, some polymer materials were also considered. The tool first estimates the required time for total part production and then calculates the total cost. The total production time is estimated based on the required machining operations, as well as drawing, programming, and machine setup time. A part complexity level was also introduced, based on the number of details and operations required for each workpiece, which will inflate the estimated times. The estimation tool was tested in a company setting, comparing the estimated operation time values with the real ones, for a wide variety of parts of differing complexity. An average error of 14% for machining operation times was registered, which is quite satisfactory, as this time is the most impactful in terms of machining cost. However, there are still some problems regarding the accuracy in estimating finishing operation times. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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