文献类型：期刊文献

英文题名：Laser additive manufacturing of CoCrNi medium entropy alloy composites reinforced by in-situ nanoprecipitations: Microstructure formation and mechanical properties

作者：Zheng, Xiaodong[1];Chen, Hongyu[1];Lu, Tiwen[2];Yao, Ning[2];Wang, Yonggang[1];Liu, Yang[1];Kosiba, Konrad[3]

机构：[1]Ningbo Univ, Key Lab Impact & Safety Engn, Minist Educ China, Ningbo 315211, Peoples R China;[2]East China Univ Sci & Technol, Key Lab Pressure Syst & Safety, Minist Educ, Shanghai 200237, Peoples R China;[3]Leibniz Inst Solid State & Mat Res Dresden, Inst Complex Mat, Helmholtzstr 20, D-01069 Dresden, Germany

年份：2024

卷号：207

外文期刊名：MATERIALS CHARACTERIZATION

收录：;EI(收录号：20234915147772);WOS:【SCI-EXPANDED(收录号:WOS:001127649500001)】；

基金：The authors are grateful for the financial support from the Zhejiang Provincial Natural Science Foundation of China under grant number LQ23E050010.

语种：英文

外文关键词：Additive manufacturing; Laser powder bed fusion; In -situ reaction; Medium entropy alloy; Microstructure; Mechanical property

摘要：The equiatomic CoCrNi medium entropy alloy (MEA) with a single-phase face-centered cubic (FCC) structure shows high toughness, but low yield strength, which limits its industrial applications. The incorporation of a finely distributed second phase preferably via an in-situ reaction during solidification would pose an efficient approach to strengthen the CoCrNi MEA. In this study, CoCrNi MEA nanocomposites were fabricated by laser powder bed fusion (LPBF) of the powder mixture, which consists of CoCrNi and Ti-6Al-4V pre-alloyed powders, as feedstock material. The results showed that the nano-sized, coherent, and uniformly distributed L12-Ni3(Ti, Al) precipitates formed in-situ during the LPBF resulting in the fabrication of CoCrNi MEA composites. Increasing addition of Ti-6Al-4V causes the precipitates to progressively segregate at the grain boundaries, an intensified lattice distortion and dislocation density as well as a morphological transformation from coarse, columnar FFC grains into fine, equiaxed grains. The resulting composites showed strengthening at the expense of ductility. At the optimum addition of 5.0 at.% Ti-6Al-4V, the resulting composite showed an excellent combination of strength and toughness with yield strength, tensile strength, and fracture elongation of-917 MPa,-1141 MPa, and-14.65%, respectively. Compared to the CoCrNi MEA, the yield strength and tensile strength increased by-262 MPa and 220 MPa, respectively. This work demonstrates that the fabrication of composites via an in-situ reaction leading to the formation of nano-precipitates embedded in the matrix poses a viable tool to effectively strengthen MEA materials.