Significance of grain refinement on micro-mechanical properties and structures of additively-manufactured CoCrFeNi high-entropy alloy
Significance of grain refinement on micro-mechanical properties and structures of additively-manufactured CoCrFeNi high-entropy alloy
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DOI：
10.1016/j.msea.2021.140898
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
W. Zhao;Jae-Kyung Han;Y. Kuzminova;S. Evlashin;A. Zhilyaev;A. Pesin;J. Jang;K. Liss;M. Kawasaki
中科院分区：
文献类型：
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作者：
W. Zhao;Jae-Kyung Han;Y. Kuzminova;S. Evlashin;A. Zhilyaev;A. Pesin;J. Jang;K. Liss;M. Kawasaki
晶粒细化是提高常规高熵合金力学性能的有效途径。HEAs的增材制造是一项新的材料挑战，越来越多的报告可用于探索最佳工艺参数和制造后处理，以提高增材制造（AM）HEAs的物理和机械性能。在AM HEAs发展的现阶段，有必要研究晶粒细化对其力学性能和结构的影响。在本研究中，一个CoCrFeNi HEA的激光粉末床熔融技术制造的预合金HEA粉末上进行晶粒细化的高压扭转下6 GPa在室温下高达8转。纳米压痕和维氏显微硬度测试的结果表明，高应变硬化能力和增加的塑性，从而潜在的高延展性，在纳米结构的AM CoCrFeNi HEA。X射线衍射分析表明，随着晶粒细化，HEA的晶粒尺寸减小，微观应变增加，晶格常数增大。结构的变化证明纳米压痕的晶界介导的位错活动的速率控制机制的纳米结构的AM HEA的估计。这项研究提供了目前的发展中的AM技术的HEAs的纳米结构的优势。
Grain refinement is an effective approach to improve mechanical properties of conventionally-manufactured high entropy alloys (HEAs). Additive manufacturing of HEAs is a new materials challenge and increasing reports are available for exploring the optimal processing parameters and post-manufacturing treatments to advance the physical and mechanical properties of additively-manufactured (AM) HEAs. At the current stage of the development of AM HEAs, it is necessary to investigate the significance of grain refinement on their mechanical properties and structures. In the present study, a CoCrFeNi HEA is manufactured by a laser powder-bed fusion technique using pre-alloyed HEA powders on which grain refinement was conducted by high-pressure torsion for up to 8 turns under 6 GPa at room temperature. The results from nanoindentation and Vickers microhardness testing demonstrate high strain hardening capability and increased plasticity, thus potentially high ductility, in the nanostructured AM CoCrFeNi HEA. X-ray diffraction analysis demonstrates the structural evolution with decreasing crystallite size, increasing microstrain and expanding lattice parameter with grain refinement in the HEA. The structural changes justify the estimation by nanoindentation of the rate-controlling mechanism of the grain boundary-mediated dislocation activity for the nanostructured AM HEA. This study provides advantages of nanostructuring for current developments in the AM technology of HEAs.