Correlation between microstructural heterogeneity and anisotropy of mechanical properties of laser powder bed fused CoCrFeMnNi high entropy alloy
Correlation between microstructural heterogeneity and anisotropy of mechanical properties of laser powder bed fused CoCrFeMnNi high entropy alloy
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DOI：
10.1016/j.msea.2022.143920
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
Chengcheng Zhang;K. Feng;H. Kokawa;Zhuguo Li
中科院分区：
文献类型：
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作者：
Chengcheng Zhang;K. Feng;H. Kokawa;Zhuguo Li
激光粉末床熔凝（LPBF）制备的面心立方（FCC）结构合金具有独特的显微组织，具有优异的力学性能，但也不可避免地导致了力学性能的各向异性。在这项研究中，分层组织和力学性能之间的关系沿着水平，对角线，和垂直方向的LPBF建立的CoCrFeMnNi高熵合金（HEA）的定性和定量研究。水平样品表现出最高的屈服强度（YS）和最低的伸长率，而垂直样品表现出最低的YS和比对角样品略低的伸长率，其几乎是水平样品的两倍。在多尺度下的显微组织特征中，柱状晶形貌和织构决定了力学性能的各向异性。首次采用体积加权（V-W）平均晶粒尺寸估算了LPBF制备的具有复杂晶粒尺寸分布的CoCrFeMnNi合金的YS和临界孪晶应力（CTS）。V-W平均晶粒尺寸在计算对角和垂直样品的YS以及沿着所有三个方向的CTS方面表现出较高的精度。对于水平试样，变形过程中晶粒形态主导于纹理，对角试样和垂直试样在变形初期也是如此。在应变后期，质地起着更重要的作用。
The unique microstructure of face-centered-cubic (FCC) structured alloys fabricated by laser powder bed fusion (LPBF) contributes to outstanding mechanical performances, but inevitably leads to anisotropy of mechanical properties. In this study, the relationship between the hierarchical microstructure and mechanical properties along the horizontal, diagonal, and vertical directions of the LPBF-built CoCrFeMnNi high entropy alloy (HEA) were qualitatively and quantitatively investigated. The horizontal samples exhibit the highest yield strength (YS) and the lowest elongation, while the vertical samples show the lowest YS and a slightly lower elongation than the diagonal samples, which are nearly two times the horizontal samples. Among the microstructural features at multiple length scales, both the columnar grain morphology and texture determine the anisotropy of mechanical properties. For the first time, the volume-weighted (V–W) average grain size was used to estimate the YS and critical twinning stress (CTS) of the LPBF-built CoCrFeMnNi alloy with a complex grain size distribution. The V–W average grain size exhibited high accuracy in calculating the YSs of the diagonal and vertical samples as well as CTSs along all the three directions. For the horizontal sample, the grain morphology dominates over texture during deformation, which is the same for the diagonal and vertical samples at the early stage of deformation. The texture plays a more important role at the late stage of straining.