On the origin and evolution of cellular structures in CoCrFeMnNi high entropy alloy fabricated by laser powder bed fusion
On the origin and evolution of cellular structures in CoCrFeMnNi high entropy alloy fabricated by laser powder bed fusion
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DOI：
10.1016/j.matchar.2022.112586
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发表时间：
2023-02
影响因子：
4.7
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
通过激光粉末床熔合（LPBF）制造的面心立方（FCC）金属中形成的独特胞状结构导致非凡的机械性能[1-3]。然而，迄今尚未就形成机制达成共识。在这项研究中，CoCrFeMnNi高熵合金（HEA）的LPBF期间的细胞结构的起源和演变进行了调查。对单轨壁和立方体中产生的胞状结构进行了表征和分析。特别是，调查和比较的形态，化学偏析，取向差，并在最后一个熔池和中间区域的建成立方体的胞状结构的位错密度。实验结果表明，Mn、Ni偏聚的化学晶胞和低位错密度晶胞同时产生，并相互重叠。随后的激光轨迹施加的多次热机械处理增加了位错密度和厚度的细胞，而不破坏细胞的形状或增加细胞壁的取向差。同时，化学细胞分离得到缓解。在演化过程中保持稳定的胞状结构的形态和分布由凝固条件决定。相对于传统的形变诱导位错结构，化学晶胞的稳定性有助于形成胞状结构的独特特征。
The unique cellular structures formed in face-centered-cubic (FCC) metals fabricated via laser powder bed fusion (LPBF) lead to extraordinary mechanical properties [1–3]. However, a consensus on the formation mechanism has not been achieved thus far. In this study, a CoCrFeMnNi high entropy alloy (HEA) was employed to investigate the origin and evolution of cellular structures during LPBF. The cellular structures generated in a single-track wall and a cube were characterized and analyzed. In particular, investigation and comparison was made of the morphology, chemical segregation, misorientation, and dislocation densities of cellular structures in the last melt pool and middle region of the as-built cube. Experimental results demonstrated that chemical cells with segregation of Mn and Ni and low dislocation-density cells were generated simultaneously and overlapped with each other. The multiple thermomechanical treatments exerted by subsequent laser tracks increased the dislocation density and thickness of the cell without destroying the cellular shapes or increasing the cell-wall misorientation. At the same time, chemical cell segregation was alleviated. The morphology and distribution of cellular structures that remain stable during evolution are determined by the solidification condition. The stability of the chemical cells contributes to the unique characteristics of cellular structures relative to conventional deformation-induced dislocation structures.