Abstract
Dual-phase high-entropy alloys (DP-HEAs) with excellent strength-ductility combinations have attracted scientific interests. In the present study, the microstructures of AlCrCuFeNi30 DP-HEA fabricated via selective laser melting (SLM) are rationally adjusted and controlled. The mechanisms engendering the hierarchical microstructures are revealed. It is found that the AlCrCuFeNi30 fabricated by SLM at the scanning speed of 400 mm s−1 falls into the eutectic coupled zone, and increasing the scanning speed will make this composition deviate away from the eutectic coupled zone due to the increased cooling rate. The enrichment of Cr and Fe solutes with large growth restriction values ahead of the solid/liquid interface can develop a constitutional supercooling zone, thus facilitating the heterogeneous nucleation and nearequiaxed grain formation. The synergy of the near-eutectic DP nano-structures and near-equiaxed grains instead of columnar ones effectively suppresses cracking for the as-built DP-HEA. During the tensile deformation, the intergranular back stress hardening similar to the grain-boundary strengthening is discovered. Meanwhile, the near-eutectic microstructures comprised of soft face-centered cubic and hard ordered body-centered cubic (B2) DP nano-structures lead to plastic strain incompatibility within grains, thus producing the intragranular back stress. The Cr-rich nano-precipitates inside the B2 phase are found to be sheared by dislocation gliding and can complement the back stress. Additionally, multiple strengthening mechanisms are physically evaluated, and the back stress strengthening contributes obviously to the high performances of the as-built DP-HEA.
摘要
双相高熵合金因具有优异的综合力学性能而备受关注. 本文 对激光选区熔化制备的AlCrCuFeNi3.0双相高熵合金微观组织进行 了调控, 揭示了分层组织形成的机理. 研究发现, 当激光扫描速度为 400 mm s−1时, AlCrCuFeNi3.0成分进入共生区, 随着扫描速度的增 加, 冷却速率增加, 该成分将偏离共生区. 固液前沿Cr和Fe溶质的 富集产生成分过冷, 有利于异质形核和等轴晶的形成. 近共晶组织 与近等轴晶的共同作用有效地抑制了开裂. 在拉伸变形过程中, 发 现了类似于晶界强化的晶间背应力强化现象. 同时, 由面心立方和 有序体心立方(B2)双相纳米结构组成的近共晶组织导致晶内塑性 变形不协调, 从而产生晶内背应力. 而B2相中富铬的纳米析出相发 生位错剪切变形, 可以强化背应力. 此外, 本文对多种强化机制进行 了物理评估, 发现背应力强化显著提高了该合金的力学性能.
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Acknowledgements
This work was supported by the Pre-research Fund Project of Ministry of Equipment and Development of China (61409230301), and the Fundamental Research Funds for the Central Universities (2019kfyXMPY005 and 2019kfyXKJC042). The authors thank the Analytical and Testing Center of HUST for SEM, EBSD, EPMA and TEM measurement.
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Wang Z conceived the experiments. Wang Z, Luo S and Su Y contributed to the theoretical analysis. Luo S performed the experiments and wrote the paper. All authors discussed the results and commented on the manuscript.
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The authors declare no conflict of interest.
Shuncun Luo received his Master’s degree from Central South University in 2017. Currently, he is a PhD candidate at Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology (HUST), China. His current research interest focuses on the laser additive manufacturing of advanced structural materials, such as high-entropy alloy and high-entropy light alloy.
Yue Su received her bachelor’s degree from Wuhan University of Science and Technology in 2018. Currently, she is a Master degree candidate at Wuhan National Laboratory for Optoelectronics, HUST, China. Her current research interest focuses on the laser additive manufacturing of high-entropy alloy.
Zemin Wang received his PhD degree in materials science from HUST in 2003. He did scientific research in the Multidisciplinary Research Center for Materials Processing at the University of Birmingham from 2007 to 2008. He has been a professor of materials science and optical engineering at HUST since 2011. His research interests include laser additive manufacturing, laser materials processing, materials science & engineering, and laser manufacturing engineering.
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Luo, S., Su, Y. & Wang, Z. Tailored microstructures and strengthening mechanisms in an additively manufactured dual-phase high-entropy alloy via selective laser melting. Sci. China Mater. 63, 1279–1290 (2020). https://doi.org/10.1007/s40843-020-1291-9
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DOI: https://doi.org/10.1007/s40843-020-1291-9