Research

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18 pages, 10422 KiB

Open AccessArticle

Diffusivities and Atomic Mobilities in BCC Ti-Fe-Cr Alloys

by Yi Huang, Jingjing Nie, Weimin Bai, Songsong Hu, Xinming Wang, Ligang Zhang and Libin Liu

Materials 2024, 17(8), 1927; https://doi.org/10.3390/ma17081927 - 22 Apr 2024

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Abstract

In this research, the diffusion behaviors within the Ti-Fe-Cr ternary system were examined at the temperatures of 1273 K and 1373 K through the diffusion couple technique. This study led to the determination of both ternary inter-diffusion and impurity diffusion coefficients in the [...] Read more.

In this research, the diffusion behaviors within the Ti-Fe-Cr ternary system were examined at the temperatures of 1273 K and 1373 K through the diffusion couple technique. This study led to the determination of both ternary inter-diffusion and impurity diffusion coefficients in the body-centered cubic (bcc) phase for the Ti-Fe-Cr alloy, utilizing the Whittle–Green and Hall methods. The statistics show that the average diffusion coefficients

{\tilde{D}}_{F e F e}^{T i}

and

{\tilde{D}}_{C r C r}^{T i}

measured at 1273 K were 1.34 × 10⁻¹² and 3.66 × 10⁻¹³, respectively. At 1373 K, the average values of

{\tilde{D}}_{F e F e}^{T i}

and

{\tilde{D}}_{C r C r}^{T i}

were 4.89 × 10⁻¹² and 1.43 × 10⁻¹². By adopting the CALPHAD method, a self-consistent database for atomic mobility in the bcc phase of the Ti-Fe-Cr system was established. This database underwent refinement by comparing the newly acquired diffusion coefficients with data from the existing literature. Diffusion simulations for the diffusion couples were performed, drawing on the established database. The error between the simulated diffusion coefficient and the experimental measurement data is within 15%, and the simulated data of the component distance distribution and diffusion path are in good agreement with the experimental data. The simulations generated results that aligned well with the observed experimental diffusion characteristics, thereby affirming the reliability and accuracy of the database. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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18 pages, 9334 KiB

Open AccessArticle

Development of Mechanical Properties of Stainless Steel 316LN-IG after Cryo-Plastic Deformation

by Alica Fedoriková, Patrik Petroušek, Tibor Kvačkaj, Róbert Kočiško and Michal Zemko

Materials 2023, 16(19), 6473; https://doi.org/10.3390/ma16196473 - 29 Sep 2023

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Abstract

The article deals with increasing the mechanical properties of stainless steel 316 Ln-IG, which is intended for work in cryogenic temperatures (liquid nitrogen and liquid helium), such as conductor conduits for the ITER magnet system. The strength and plastic properties were increased by [...] Read more.

The article deals with increasing the mechanical properties of stainless steel 316 Ln-IG, which is intended for work in cryogenic temperatures (liquid nitrogen and liquid helium), such as conductor conduits for the ITER magnet system. The strength and plastic properties were increased by a combination of cold and cryo-rolling and heat treatment. The mechanical properties of rolled material were investigated at 293 K, 77 K, and 4.2 K. The work-hardening rate of the steel increased continuously with a lowering of the temperature. The maximum yield strength and ultimate tensile strength were achieved by the cryo-rolling process with a total thickness deformation of 50%. The material properties tested at ambient temperature were 0.2YS = 1050 MPa, UTS = 1200 MPa, and at 4.2 K, the values were 0.2YS = 1804 MPa and UTS = 2081 MPa. Two types of long-term heat treatment were applied after experimental rolling (823 K and 1093 K for 10 h). The highest precipitation hardening of steel was achieved at a temperature of 823 K after 50% deformation. The resulting grain size decreased from the initial 216 μm (before the rolling process) to 70 μm after ambient rolling and 72 μm after cryo-rolling. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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25 pages, 9267 KiB

Open AccessArticle

Multi-Objective Optimization of The Low-Pressure Casting of Large-Size Aluminum Alloy Wheels through a Systematic Optimization Idea

by Yuhang He, Dehong Lu, Zhenming Li and Donghui Lu

Materials 2023, 16(18), 6223; https://doi.org/10.3390/ma16186223 - 15 Sep 2023

Viewed by 953

Abstract

The process parameters in the low-pressure casting of large-size aluminum alloy wheels are systematically optimized in this work using numerical casting simulation, response surface methodology (RSM), and genetic algorithm (NSGA-II). A nonlinear input–output relationship was established based on the Box–Behnken experimental design (BBD) [...] Read more.

The process parameters in the low-pressure casting of large-size aluminum alloy wheels are systematically optimized in this work using numerical casting simulation, response surface methodology (RSM), and genetic algorithm (NSGA-II). A nonlinear input–output relationship was established based on the Box–Behnken experimental design (BBD) for the crucial casting parameters (pouring temperature, mold temperature, holding pressure, holding time), and response indicators (defect volume fraction, spokes large plane mean secondary dendrite spacing (SDAS)), and a mathematical model was developed by regression analysis. The Isight 2017 Design Gateway and NSGA-II algorithm were used to increase the population and look for the best overall solution for the casting parameters. The significance and predictive power of the model were assessed using ANOVA. Casting numerical simulation was used to confirm the best option. To accomplish systematic optimization in its low-pressure casting process, the mold cooling process parameters were adjusted following the local solidification rate. The results showed that the mathematical model was reliable. The optimal solutions were a pouring temperature of 703 °C, mold temperature of 409 °C, holding pressure of 1086 mb, and holding time of 249 s. The mold cooling process was further optimized, and the sequence solidification of the optimal solution was realized under the optimized cooling process. Finally, the wheel hub was manufactured on a trial basis. The X-ray detection, mechanical property analysis, and metallographic observation showed that the wheel hub had no X-ray defects and its mechanical properties were well strengthened. The effectiveness of the system optimization process scheme was verified. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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13 pages, 4540 KiB

Open AccessArticle

Formation and Evolution Mechanism of Intermetallic Compounds of Friction Stir Lap Welded Steel/Aluminum Joints

by Yongzhi Liu, Qiu Pang, Zhichao Zhang and Lan Hu

Materials 2023, 16(18), 6118; https://doi.org/10.3390/ma16186118 - 07 Sep 2023

Cited by 1 | Viewed by 713

Abstract

Interfacial layers with brittle intermetallic compounds (IMC) greatly influence the performance of steel–aluminum friction stir lap welding (FSLW) joints. Thus, the formation and evolution of IMC between 7075-T6 aluminum alloy and galvanized DP590 steel in steel–aluminum FSLW joints were investigated. An FSLW numerical [...] Read more.

Interfacial layers with brittle intermetallic compounds (IMC) greatly influence the performance of steel–aluminum friction stir lap welding (FSLW) joints. Thus, the formation and evolution of IMC between 7075-T6 aluminum alloy and galvanized DP590 steel in steel–aluminum FSLW joints were investigated. An FSLW numerical model was developed using the computational fluid dynamics method to analyze the interface temperature between the aluminum alloy and steel. Scanning electron microscopy (SEM) was conducted to observe the microstructure characterization and measure the IMC thickness. Phases among different joint zones were analyzed by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). IMC layer formation was predicted by the effective Gibbs free energy model presented in this paper according to thermodynamic principles. The Monte Carlo method was utilized to predict the thickness of IMC layers. It was found that the IMC layer at the interface of the welded joint is composed of Fe₂Al₅, FeAl₃, and Al-Zn eutectic. The IMC thickness decreased from 4.3 μm to 0.8 μm with the increasing welding speed, which was consistent with the Monte Carlo simulation results. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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16 pages, 10300 KiB

Open AccessEditor’s ChoiceArticle

Investigation of Pre-Aged Hardening Single-Point Incremental Forming Process and Mechanical Properties of AA6061 Aluminum Alloy

by Yao Zhang, Zhichao Zhang, Yan Li, Lan Hu, Qiu Pang and Zhili Hu

Materials 2023, 16(11), 4154; https://doi.org/10.3390/ma16114154 - 02 Jun 2023

Cited by 1 | Viewed by 1206

Abstract

Currently, the single-point incremental forming process often faces issues such as insufficient formability of the sheet metal and low strength of the formed parts. To address this problem, this study proposes a pre-aged hardening single-point incremental forming (PH-SPIF) process that offers several notable [...] Read more.

Currently, the single-point incremental forming process often faces issues such as insufficient formability of the sheet metal and low strength of the formed parts. To address this problem, this study proposes a pre-aged hardening single-point incremental forming (PH-SPIF) process that offers several notable benefits, including shortened procedures, reduced energy consumption, and increased sheet forming limits while maintaining high mechanical properties and geometric accuracy in formed components. To investigate forming limits, an Al-Mg-Si alloy was used to form different wall angles during the PH-SPIF process. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) analyses were conducted to characterize microstructure evolution during the PH-SPIF process. The results demonstrate that the PH-SPIF process can achieve a forming limit angle of up to 62°, with excellent geometric accuracy, and hardened component hardness reaching up to 128.5 HV, surpassing the strength of the AA6061-T6 alloy. The DSC and TEM analyses reveal numerous pre-existing thermostable GP zones in the pre-aged hardening alloys, which undergo transformation into dispersed β” phases during the forming procedure, leading to the entanglement of numerous dislocations. The dual effects of phase transformation and plastic deformation during the PH-SPIF process significantly contribute to the desirable mechanical properties of the formed components. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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16 pages, 15700 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Gradient Interfaces in Wire Arc Additive Remanufacturing of Hot Forging Die Steel

by Mao Ni, Zeqi Hu, Xunpeng Qin, Xiaochen Xiong and Feilong Ji

Materials 2023, 16(7), 2639; https://doi.org/10.3390/ma16072639 - 27 Mar 2023

Cited by 4 | Viewed by 1575

Abstract

Hot forging dies are subjected to periodic thermal stress and often fail in the forms of thermal fatigue, wear, plastic deformation, and fracture. A gradient multi-material wire arc additive remanufacturing method for hot forging dies was proposed to extend the service life of [...] Read more.

Hot forging dies are subjected to periodic thermal stress and often fail in the forms of thermal fatigue, wear, plastic deformation, and fracture. A gradient multi-material wire arc additive remanufacturing method for hot forging dies was proposed to extend the service life of hot forging dies and reduce total production costs. The properties of multi-material gradient interfaces play a critical role in determining the overall performance of the final products. In this study, the remanufacturing zone of a hot forging die was divided into three deposition layers: the transition layer, the intermediate layer, and the strengthening layer. Experiments of wire arc additive manufacturing with gradient material were conducted on a 5CrNiMo hot forging die steel. The microstructure, microhardness, bonding strength, and impact property of gradient interfaces were characterized and analyzed. The results revealed that the gradient additive layers and their interfaces were defect-free and that the gradient interfaces had obtained a high-strength metallurgical bonding. The microstructure of the gradient additive layers presented a gradient transformation process of bainite-to-martensite from the bottom to the top layer. The microhardness gradually increased from the substrate layer to the surface-strengthening layer, forming a three-level gradient in the range of 100 HV. The impact toughness values of the three interfaces were 46.15 J/cm², 54.96 J/cm², and 22.53 J/cm², and the impact fracture morphology ranged from ductile fracture to quasi-cleavage fracture. The mechanical properties of the gradient interfaces showed a gradient increase in hardness and strength, and a gradient decrease in toughness. The practical application of hot forging die remanufactured by the proposed method had an increase of 37.5% in average lifespan, which provided scientific support for the engineering application of the gradient multi-material wire arc additive remanufacturing of hot forging dies. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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23 pages, 20204 KiB

Open AccessArticle

A Tailored Preparation Method of Variable Strength for Ultra-High-Strength Steel Sheet and Mapping Mechanism between Process and Property

by Guo-Zheng Quan, Yan-Ze Yu, Yu Zhang, Yu-Qing Zhang and Wei Xiong

Materials 2022, 15(19), 6620; https://doi.org/10.3390/ma15196620 - 23 Sep 2022

Cited by 1 | Viewed by 1039

Abstract

The spatiotemporal phase transformation during hot stamping would considerably effect the microstructure and mechanical properties of steels. In order to manufacture hot-stamping components of ultra-high-strength steel with tailored mechanical properties, the effect of the quenching time and the temperature of the die on [...] Read more.

The spatiotemporal phase transformation during hot stamping would considerably effect the microstructure and mechanical properties of steels. In order to manufacture hot-stamping components of ultra-high-strength steel with tailored mechanical properties, the effect of the quenching time and the temperature of the die on the phase-transformation characteristics and mechanical property of ultra-high-strength steel was deeply studied. A finite element (FE) model coupled with a thermomechanical phase was employed to perform a succession of simulations for hot stamping corresponding to different quenching times and the temperatures of die, and the corresponding hot stamping experiments were performed. The 3D mapping surfaces of the temperature; quenching time; and three microstructures, namely austenite, bainite, and martensite, were constructed, and the mapping relationships in such surfaces were further explained by microstructural observations. Subsequently, based on the test results of the mechanical properties, the relationship curves of hardness and tensile strength, hardness, and elongation at break were fitted respectively, and then the 3D mapping surfaces were constructed for hardness, tensile strength, and elongation at break, which varied with the temperature die and quenching time. Finally, the quenching parameters of the automobile B-pillar were designed according to the constructed mapping relationship, and the hot-stamping FE simulation of the automobile B-pillar was developed. The result shows that those constructed mapping surfaces are helpful for adjusting the local mechanical property of the steels by designing the parameters. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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Review

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30 pages, 12121 KiB

Open AccessReview

Recent Progress on Regulating Strategies for the Strengthening and Toughening of High-Strength Aluminum Alloys

by Jia Zheng, Qiu Pang, Zhili Hu and Qian Sun

Materials 2022, 15(13), 4725; https://doi.org/10.3390/ma15134725 - 05 Jul 2022

Cited by 8 | Viewed by 2583

Abstract

Due to their high strength, high toughness, and corrosion resistance, high-strength aluminum alloys have attracted great scientific and technological attention in the fields of aerospace, navigation, high-speed railways, and automobiles. However, the fracture toughness and impact toughness of high-strength aluminum alloys decrease when [...] Read more.

Due to their high strength, high toughness, and corrosion resistance, high-strength aluminum alloys have attracted great scientific and technological attention in the fields of aerospace, navigation, high-speed railways, and automobiles. However, the fracture toughness and impact toughness of high-strength aluminum alloys decrease when their strength increases. In order to solve the above contradiction, there are currently three main control strategies: adjusting the alloying elements, developing new heat treatment processes, and using different deformation methods. This paper first analyzes the existing problems in the preparation of high-strength aluminum alloys, summarizes the strengthening and toughening mechanisms in high-strength aluminum alloys, and analyzes the feasibility of matching high-strength aluminum alloys in strength and toughness. Then, this paper summarizes the research progress towards adjusting the technology of high-strength aluminum alloys based on theoretical analysis and experimental verification, including the adjustment of process parameters and the resulting mechanical properties, as well as new ideas for research on high-strength aluminum alloys. Finally, the main unsolved problems, challenges, and future research directions for the strengthening and toughening of high-strength aluminum alloys are systematically emphasized. It is expected that this work could provide feasible new ideas for the development of high-strength and high-toughness aluminum alloys with high reliability and long service life. Full article

(This article belongs to the Special Issue High-Performance Light Materials for Automobile and Aerospace Applications)

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