Microstructure transition and mechanical properties of friction stir processed CoCrFeMnNi high entropy alloy fabricated by laser powder bed fusion
Microstructure transition and mechanical properties of friction stir processed CoCrFeMnNi high entropy alloy fabricated by laser powder bed fusion
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DOI：
10.1016/j.msea.2022.143254
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
Chengcheng Zhang;K. Feng;H. Kokawa;Zhuguo Li;Ke Chen
中科院分区：
文献类型：
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作者：
Chengcheng Zhang;K. Feng;H. Kokawa;Zhuguo Li;Ke Chen
采用搅拌摩擦工艺（FSP）对激光粉末床熔凝（LPBF）制备的CoCrFeMnNi合金进行表面改性，研究了FSP过程中晶粒结构、位错结构和织构的演变以及动态再结晶（DRX）机制。结果表明，连续动态再结晶（CDRX）和不连续动态再结晶（DDRX）同时发生，使平均晶粒尺寸从15.4 μm细化到4.8 μm，搅拌区（SZ）晶粒尺寸和面积分布更加均匀。由于材料流动和摩擦热的不均匀分布，热机械影响区（TMAZ）呈现出组织梯度，整个SZ的晶粒结构是不均匀的。分析了FSP区组织与力学性能的关系。SZ的硬度和屈服强度（YS）（分别为190 ± 3 HV和501 ± 2 MPa）低于LPBF材料的硬度和屈服强度（分别为229 ± 10 HV和563 ± 3 MPa）。另一方面，伸长率从23.8 ± 0.4%增加到37.5 ± 0.3%，而极限拉伸强度（UTS）从665 ± 5MPa增加到719 ± 3MPa。在FSP后的SZ中实现了比LPBF构建的CoCrFeMnNi合金更好的强度和延展性的组合。
In this work, Friction stir processing (FSP) was conducted on the CoCrFeMnNi alloy fabricated via laser powder bed fusion (LPBF) to modify the surface microstructure, during which the evolution of grain structures, dislocation structures, and texture as well as the dynamic recrystallization (DRX) mechanism were investigated. The experimental results demonstrated that continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occurred simultaneously to refine the average grain size from 15.4 μm to 4.8 μm, while the distribution of grain size and area became more uniform in the stir zone (SZ). Due to the inhomogeneous distribution of material flow and friction heat, the thermo-mechanically affected zone (TMAZ) exhibits microstructure gradients and the grain structures are nonuniform throughout the SZ. In addition, the relationship between the microstructure and mechanical properties of the FSP region was analyzed. The hardness and yield strength (YS) of the SZ (∼190 ± 3 HV and 501 ± 2 MPa, respectively) are lower than those of the LPBF material (∼229 ± 10 HV and 563 ± 3 MPa, respectively). On the other hand, the elongation increased from 23.8 ± 0.4% to 37.5 ± 0.3%, while the ultimate tensile strength (UTS) increased from 665 ± 5 MPa to 719 ± 3 MPa. A better combination of strength and ductility than the LPBF-built CoCrFeMnNi alloy was achieved in the SZ after FSP.