Additively manufactured high strength and ductility CrCoNi medium entropy alloy with hierarchical microstructure
Additively manufactured high strength and ductility CrCoNi medium entropy alloy with hierarchical microstructure
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DOI：
10.1016/j.msea.2021.141545
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Bo-kyeong Han;Chengcheng Zhang;K. Feng;Zhuguo Li;Xiancheng Zhang;Yao Shen;Xiaodong Wang;H. Kokawa
中科院分区：
文献类型：
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作者：
Bo-kyeong Han;Chengcheng Zhang;K. Feng;Zhuguo Li;Xiancheng Zhang;Yao Shen;Xiaodong Wang;H. Kokawa
CrCoNi中熵合金（MEA）是一种具有上级低温力学性能的新型材料。在这项工作中，我们通过选择性激光熔化（SLM）制造了近全致密的分级CrCoNi MEA，并在77 K下实现了860 MPa的上级屈服强度，超过了传统制造的对应物，除了合理的延展性。随着温度的降低，强度和塑性增加，在77 K下达到1340 MPa的极限抗拉强度和47%的延伸率。EBSD、TEM和原位同步辐射X射线衍射（SXRD）拉伸试验表明，该合金的高强度来源于复杂的异质柱状晶内由高密度位错形成的胞状结构和小角度晶界（LAGB）组成的分级组织，原位SXRD拉伸实验和形变后TEM及EBSD分析表明，SLM-100纳米晶的纳米孪晶响应与形变后的纳米晶的孪晶响应一致，并与理论计算结果进行了比较。高密度LAGB和近生长织构都抑制了CrCoNi MEA的生成<100>。结果表明，SLM是一种可行的技术，用于制造致密的分层CrCoNi MEA，并提出了一种设计策略，以进一步提高机械性能。
The CrCoNi medium entropy alloy (MEA) is a technologically intriguing material showing superior cryogenic mechanical properties. In this work, we fabricated near full-dense hierarchical CrCoNi MEA via selective laser melting (SLM) and achieved superior yield strength of 860 MPa at 77K that surpasses that of conventionally fabricated counterparts, in addition to reasonable ductility. The strength and ductility increase as temperature drops, reaching a 1340 MPa ultimate tensile strength and a 47% elongation at 77K. EBSD, TEM, andin-situsynchrotron X-ray diffraction (SXRD) tensile tests disclose that the high strength stems from the hierarchical microstructure composed of high-density dislocations-formed cellular structures and low-angle grain boundaries (LAGB) within the complex heterogeneous columnar grains, and further validated by theoretical calculation.In-situSXRD tensile tests and post-deformation TEM and EBSD reveal that nano-twinning response in the SLM-built CrCoNi MEA is suppressed by both high-density LAGB and near <100> growth texture. The results demonstrate that SLM is a viable technique for fabricating dense hierarchical CrCoNi MEA and suggest a design strategy to improve mechanical properties further.