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Numerical simulation of microstructure and microporosity morphology in directional solidification of aluminum-copper alloys:Effect of copper content and withdrawal rate

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China Foundry 2025年第1期22卷 33-44页

作者： Wei Yuan Hai-dong Zhao Xu Shen Chun Zou Yuan Liu Qing-yan Xu National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials South China University of TechnologyGuangzhou 510640China Key Laboratory for Advanced Materials Processing Technology(Ministry of Education) Tsinghua UniversityBeijing 100084China

Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys,considering variations in Cu content and solidification *** results indicate that the Cu content primarily influences the growth of *** validate the model,directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal *** experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model,thus confirming the validity of the *** alloy’s liquidus temperature,dendrite morphology,and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity *** withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates,resulting in different microporosity characteristics.

关键词： microporosity dendrites cellular automaton Al-Cu alloys directional solidification

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Disrupting variant selection memory effect in laser powder bed fusion to improve strength-ductility synergy of Ti-6Al-4V alloys

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Journal of materials Science and Technology 2025年 219卷 19-32页

作者： Yang, C. Liu, B. Pan, L.L. Yang, Y. Zhou, Y. Cai, W.S. Liu, Le-hua National Engineering Research Center of Near-net-shape Forming for Metallic Materials Guangdong Provincial Key Laboratory for Processing and Forming of Advanced Metallic Materials South China University of Technology Guangzhou 510640 China Shenzhen Leadwell Technology Co. Ltd. Shenzhen Guangdong 518000 China

Texture formation is frequently observed in parts produced by Laser Powder Bed Fusion (L-PBF), which can induce anisotropy and may potentially degrade plasticity. In this study, we introduce a laser remelting strategy to mitigate these adverse effects. By employing experimental observations and numerical simulations, we established the relationship between melt pool thermal history, variant selection, and mechanical properties. Our results indicate that the strengthening of texture can be prevented by disrupting the variant selection memory effect when there is a difference in scanning speeds between the printing and remelting lasers. The achieved random variant orientation is attributed to the altered cooling rates and temperature gradient directions during solidification across different layers. The optimized Ti-6Al-4V alloy demonstrates high strength (1211.5 ± 13.3 MPa) and significant elongation (12.3 % ± 0.8 %), exhibiting a superior strength-ductility synergy compared to samples produced by direct printing or laser remelting with consistent parameters, as well as most reported L-PBF processed Ti-6Al-4V alloys. Our findings provide new insights into phase transformation kinetics in L-PBF of Ti-6Al-4V alloys and facilitate the optimization of this process for manufacturing high-performance components. © 2024

关键词： Titanium alloys

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Second nearest-Neighbor Modified Embedded Atom Method Interatomic Potential for Cu-Ni-Sn Ternary System

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Computers, materials & Continua 2025年第4期83卷 65-77页

作者： Jialiang Dong Xuemao Dong Zhongxue Feng Caiju Li Jianhong Yi Jun Tan School of Materials Science and Engineering Guizhou Minzu UniversityGuiyang550025China Guangdong Key Laboratory for Advanced Metallic Materials Processing and Forming National Engineering Research Center of Near-Net-Shape Forming for Metallic MaterialsSouth China University of TechnologyGuangzhou510640China Faculty of Electronic and Information Engineering Anshun UniversityAnshun561000China Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming650093China College of Materials Science and Engineering Chongqing UniversityChongqing400044China

To explore atomic-level phenomena in the Cu-Ni-Sn alloy,a second nearest-neighbor modified embedded-atom method(2NN MEAM)potential has been developed for the Cu-Ni-Sn system,building upon the work of other *** potential demonstrates remarkable accuracy in predicting the lattice constant,with a relative error of less than 0.5%when compared to density functional theory(DFT)results,and it achieves a 10%relative error in the enthalpy of formation compared to experimental data,marking substantial advancements over prior *** bulk modulus is predicted with a relative error of 8%compared to ***,the potential effectively simulates the processes of melting and solidification of Cu-15Ni-8Sn,with a simulated melting point that closely aligns with the experimental value,within a 7.5%*** serves as a foundation for establishing a 2NN MEAM potential for a flawless Cu-Ni-Sn system and its microalloying systems.

关键词： 2NN MEAM Cu-Ni-Sn interatomic potential atomistic simulation

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Effect of vanadium on Fe-rich intermetallics in HVDC Al-8Si-0.2Mg-0.3Fe alloys

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materials Today Communications 2025年 46卷

作者： Guo, Luming Zheng, Huiting Wang, Xueling Fu, Junjie Zhao, Haidong National Engineering Research Center of Near-net Shape Forming for Metallic Materials South China University of Technology Guangzhou510641 China

The formation and evolution of Fe-rich intermetallics in Al-8Si-0.2Mg-0.3Fe-xMn-(0.6-x)V (x = 0.3, 0.4, 0.5, 0.6) alloy produced by high vacuum die casting (HVDC) process were systemically investigated by experiments and first-principles calculations. The results showed that as the V content increased, both the size of (α-Fe)Ⅰ intermetallics formed in the shot sleeve at a lower cooling rate and the clustering of (α-Fe)Ⅱ intermetallics formed in the die cavity at a higher cooling rate decreased. Adding V enhanced the nucleation of (α-Fe)Ⅱ intermetallics but inhibited their growth. The cohesion energies of α-Al(Mn, Fe)Si and α-Al(Mn, Fe, V)Si were −4.10 eV/atom and −2.97 eV/atom, respectively. The α-Al(Mn, Fe)Si structure was more stable than that of α-Al(Mn, Fe, V)Si. The diminished interatomic bonding strength between Mn and the surrounding Al or Si atoms made the α-Al(Mn, Fe, V)Si phase more susceptible to instability. Compared with the α-Al(Mn, Fe)Si phase, it was easier for α-Al(Mn, Fe, V)Si to form at a lower temperature. Adding V significantly improved the stability of the Al-Fe and Si-Fe bonds. This allowed α-Al(Mn, Fe, V)Si to consume a large number of Fe atoms during the solidification process. Therefore, the final fraction of Fe-rich intermetallics decreased with the addition of V. © 2025 Elsevier Ltd

关键词： Magnesium alloys

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Effect of retained ferrite on hydrogen embrittlement resistance of medium-carbon steel via rapid induction heating 5

Effect of retained ferrite on hydrogen embrittlement resista...

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2024 5th International Conference on Advanced materials and Intelligent Manufacturing, ICAMIM 2024

作者： Ye, Haixiao Li, Liejun Xiong, Zhitao Chen, Songjun Peng, Zhengwu National Engineering Research Center for Metal Materials Near Net Forming Technology South China University of Technology Guangzhou510640 China

This study examines the influence of retained ferrite on the hydrogen embrittlement resistance of medium-carbon steel processed via rapid induction heat treatment, in comparison to tubular furnace treatment. Microstructural analysis indicates that samples subjected to rapid induction heating retain approximately 10% ferrite, while those treated in the tubular furnace are primarily martensitic. The former exhibits superior resistance to hydrogen embrittlement, with minimal strength and ductility loss after short hydrogen charging. This improvement is attributed to ferrite's role in providing irreversible hydrogen traps and alleviating residual stresses within tempered martensite. The fractographic analysis further confirms a shift from ductile to brittle fracture under prolonged hydrogen exposure, underscoring ferrite's beneficial effect in mitigating embrittlement. 2025 Published under licence by IOP Publishing Ltd.

关键词： Hydrogen embrittlement

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Investigation of the synergistic evolution of mechanical properties governed by composition–process–microstructure coupling in ultra-long flow die-cast aluminum alloys

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Journal of Manufacturing Processes 2025年 145卷 508-521页

作者： Yang, Dong Tan, Yunxiang Liao, Pingwei Jiang, Daxiu Wu, Xinxing Wang, Xuefeng Zhao, Haidong Han, Zhiqiang Min, Junying Xu, Qingyan School of Mechanical Engineering Tongji University Shanghai201804 China Xiaomi Automobile Technology Co. Ltd. Beijing100176 China Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University Beijing100084 China National Engineering Research Center of Near-Net-Shape for Metallic Materials South China University of Technology Guangzhou510640 China

Giga casting technology has become integral to automotive lightweight manufacturing, yet current studies mainly address small-scale castings with limited dimensions and moderate casting parameters, leaving substantial gaps in knowledge regarding ultra-large-scale integrated die-cast aluminum components. To address this, we present a comprehensive investigation of an S-profile structural casting with a record-setting flow length of 3500 mm, manufactured via high-vacuum die-casting under an 1800-ton clamping force. Comprehensive experimental methodologies were employed to systematically evaluate the effects of alloy composition, flow length, wall thickness, filling time, die temperature, and casting pressure on the microstructural characteristics, defect formation, and resultant mechanical properties. Key findings revealed that flow length significantly affects microstructural uniformity and porosity distribution: pore sizes drastically increased from negligible at 1000 mm to approximately 100 μm at 3000 mm, accompanied by reductions in yield strength (from 108.69 MPa to 96.63 MPa), ultimate tensile strength (from 226.58 MPa to 189.46 MPa), and elongation (from 10.58 % to 3.05 %). Additionally, alloy composition critically influenced mechanical behavior;Alloy C, containing higher Si (8.0–8.5 wt%) and moderate Cu (0.1–0.5 wt%), exhibited the highest yield strength (122.81 MPa) but lower ductility (5.29 % elongation) and significant variability in tensile strength. Conversely, Alloy B provided balanced properties, achieving an optimal combination of strength (UTS ~249.26 MPa, YS ~116.31 MPa) and ductility (elongation ~6.34 %). Random forest regression analysis further identified material composition as the predominant influencing factor for strength attributes (importance scores of 0.69 for YS and 0.36 for UTS), while emphasizing the critical influence of flow length on ductility (importance score of 0.92). These insights establish a robust theoretical foundation for op

关键词： Aluminum alloys

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Tailoring grain and intermetallic of as-extruded Al-La-Mg-Fe alloy: Towards a balance of mechanical properties at room and elevated temperatures

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Journal of materials research and Technology 2025年 36卷 7615-7627页

作者： Tao Ban Zhi Wang Liejun Li Zhuoran Li Jixiang Gao Xinkui Zhang Zhengwu Peng National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials South China University of Technology Guangzhou 510640 China Guangdong Polytechnic Normal University Guangzhou 510635 China

This study successfully develops a novel Al-La-Mg-Fe alloy with a balance of room-temperature and high-temperature mechanical properties through precise control of grain structure and intermetallics via hot extrusion process. The as-extruded Al-La-Mg-Fe alloys achieve enhanced room-temperature mechanical properties (UTS: 293 ± 13 MPa, El: 6.6 ± 0.3 %) coupled with remarkable high-temperature strength-ductility synergy (UTS: 158 ± 5 MPa, El: 24.7 ± 3.0 %). The enhanced room-temperature strength-ductility balance originates from the synergistic effects of refined grains, finely dispersed intermetallics, and narrowed intermetallic-free zones, which collectively enhance dislocation motion resistance and promote dislocation accumulation. Moreover, the combined influence of high volume fraction of coarsening-resistant Al 11 La 3 and Al 13 Fe 4 intermetallics and optimized grain boundary density effectively mitigates the detrimental effects of enhanced atomic diffusion and accelerated grain boundary migration at elevated temperatures, resulting in a 54 % strength retention at 300 °C and demonstrating exceptional high-temperature mechanical performance. Additionally, the crack-buffering zones and blunting mechanisms during high-temperature tensile deformation significantly enhance the plasticity of the alloy. These findings establish fundamental principles for the coordinated optimization of grain size and intermetallics in developing heat-resistant aluminum alloys.

关键词： Al-La-Mg-Fe alloy Hot extrusion Mechanical properties High-temperature performance

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Microstructure and brazing properties of Ag20Cu35Zn(43.5-x-y)MnxSnyNi1.5 foil-filler brazing alloy

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Hanjie Xuebao/Transactions of the China Welding Institution 2025年第4期46卷 103-115页

作者： Wang, Xuecheng Fan, Jiafeng Li, Xiaoqiang Qian, Hao Xu, Changyu National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials South China University of Technology Guangzhou510641 China China Railway 18th Bureau Group Co. Ltd Tianjin300222 China

The influence of the addition of Mn and Sn elements on the microstructure, melting characteristics, and wettability of low-silver Ag20Cu35Zn(43.5-x-y)MnxSnyNi1.5 brazing alloys was investigated, and the content of Mn and Sn elements in the brazing alloys was optimized. Subsequently, the Ag20Cu35Zn31Mn10Sn2.5Ni1.5 foil-filler brazing alloy was prepared using a single roller cold method. Its performance in connecting YG15 cemented carbide and 42CrMo dissimilar steel material was then investigated through high-frequency induction brazing at 790 ~ 870 ℃. The results showed that an increase in Sn element content lead to the coarse brittle phases with a high volume fraction in the brazing alloy, and the types of the brittle phase were diversified. An increase in Mn element content caused the brazing alloys to undergo brittle phase refinement, elevation of the solidus, and a reduction in the melting range, displaying a trend of increasing and then decreasing surface areas of YG15 and 42CrMo. Optimal comprehensive properties of the brazing alloy are observed when the mass fraction of Sn and Mn elements was 2.5% and 10%, respectively. The joint shear strength between YG15 and 42CrMo brazed with Ag20Cu35Zn31Mn10Sn2.5Ni1.5 foil-filler brazing alloy at a temperature of 830 ℃ reached a maximum value of 270.36 MPa. The shear strength was comparable to that brazed with commercial Ag30CuZn brazing alloy at 850 ℃. The shear fracture was in the weld, and the fracture was a mixture of ductile fracture and partial brittle fracture. © 2025 Harbin research Institute of Welding. All rights reserved.

关键词： Brittle fracture

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Study on the Inherent Correlation Between Tensile and Impact Properties of Al-Si-Mg Alloy with the Assistance of Machine Learning

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Journal of materials engineering and Performance 2025年 1-13页

作者： Ma, Jiale Zheng, Xiongling Zhang, Wenchao Xu, Qingyan Zhao, Haidong Han, Zhiqiang School of Materials Science and Engineering Tsinghua University Beijing100084 China Tsinghua University Beijing100084 China National Engineering Research Center of Near-net-shape Forming for Metallic Materials South China University of Technology Guangzhou510000 China

It is critical to gain a quantifiable understanding of the inherent correlation between tensile and impact properties in order to effectively design alloys with high impact toughness based on available tensile property data. Machine learning methods excel at handling complex, nonlinear, and multidimensional problems, which is a feasible way to uncover the inherent correlation between tensile and impact properties. In the present study, the microstructure, mechanical properties (including tensile and impact properties), and fracture behavior of Sr- and La-modified Al-Si-Mg alloys in different aging states were investigated. Fractographic analyses were performed to study the different fracture mechanisms of quasi-statically deformed tensile specimens and dynamically deformed Charpy impact specimens. Based on the experimental data, an effective and interpretable machine learning model describing the inherent correlation between tensile and impact properties of Al-Si-Mg alloys was established. Further, Shapley additive explanations and sensitivity analyses were used to identify the significant features affecting the impact property. It can be concluded that the elongation of the Al-Si-Mg alloys plays a dominant role in influencing the impact properties. When it is not feasible to enhance both strength and ductility simultaneously, increasing ductility via a moderate reduction in strength is an effective strategy to improve impact toughness. This study offers a new perspective on heat treatment processes optimization and alloy design to develop alloys with superior impact toughness. © ASM International 2025.

关键词： Tensile strength

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Vacuum-assisted HPDC lightweight Al-based entropy alloy with ultrahigh strength and exceptional thermal stability at elevated temperatures

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materials Science and engineering: A 2025年 935卷

作者： Bai, Wenhui Zhao, Haidong Chen, Bo Xu, Qingyan Han, Zhiqiang National Engineering Research Center of Near-net-shape Forming for Metallic Materials South China University of Technology Guangzhou510640 China School of Materials Science and Engineering Tongji University Shanghai 201804 China Tsinghua University Beijing100084 China

Lightweight and high-strength aluminum (Al) alloys have a wide range of industrial applications. Al alloys with excellent elevated-temperature mechanical properties have been increasingly in demand. In this study, a novel lightweight Al-based entropy alloy (Al80Si8Mg4Cu4Zn4) with a density of 2.928 g/cm3 was calculated with thermodynamic parameters and a calculated phase diagram (CALPHAD) framework. The alloy fabricated by vacuum-assisted high pressure die casting (HPDC) shows ultrahigh specific yield strength at room and elevated temperatures (200°C-400 °C) compared with conventional Al alloys, Al-based entropy alloys, and even additive manufacturing (AM) Al alloys. Specifically, the yield strength reaches 332 MPa and 178 MPa at 300 °C and 400 °C with plasticity exceeding 40 % under compression test. At room temperature, the main strengthening mechanism is solid solution strengthening, while at elevated temperature, the primary strengthening mechanism is Orowan strengthening. The high interconnectivity of the rigid Q-Al5Cu2Mg8Si6 phase and θ-Al2Cu networks play a significant role in strengthening at the elevated temperatures. In addition, the alloy exhibits superior thermal stability. Accordingly, the estimated grain growth exponent n of ∼4.13 indicates the diffusion mechanism of the alloy is grain boundary (GB) diffusion at 300 °C. The stability is mainly attributed to the pinning effect of T-AlZnMgCu phase and the nonequilibrium segregation of Zn and Cu at GB at 300 °C and below. Moreover, stability of the size, volume fraction and hardness of intermetallic compounds (IMCs) underscores the good thermal stability of microstructure. Our findings provide an important route to fabricate the lightweight Al-based entropy alloys components with enhanced room and elevated-temperature mechanical properties by vacuum-assisted HPDC and also could promote the entropy alloy applications. © 2025

关键词： Compression testing

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