期刊
COMPOSITES PART B-ENGINEERING
卷 216, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.compositesb.2021.108837
关键词
Medium entropy alloy; Laser aided additive manufacturing; Oxide; Cryogenic properties; Microstructure
资金
- Agency for Science, Technology and Research (A*Star), Republic of Singapore [A1893a0031]
The study found that the variation in oxide content in CoCrNi medium entropy alloys affects their cryogenic tensile properties. Oxides have a certain impact on the mechanical properties of the alloy, while twin boundaries play a compensatory role in performance. Additionally, the mechanical properties are improved at low temperatures.
The CoCrNi medium entropy alloy with different amounts of oxides was fabricated by laser aided additive manufacturing (LAAM). The cryogenic tensile properties and microstructure evolution during tensile deformation were investigated. For the Sample B with higher oxide content (2.03 vol%), the yield strength (YS), ultimate tensile strength (UTS) and elongation (El) were all inferior to those of the Sample A with much fewer oxides (0.47 vol%). The lower YS of Sample B was mainly attributed to the lower initial dislocation density. The oxides contributed slightly to the increase in YS, while reducing the El significantly. The El of Sample B was comparable at 298 K and 143 K, owing to the compensation effect from twin boundaries (TBs). Higher YS and UTS were obtained at 143 K for both samples. With decreasing temperature from 298 K to 143 K, the YS and UTS of Sample A increased almost linearly, whereas the El decreased. Though a large amount of TBs were formed during the tensile deformation, they were unevenly distributed among the grains near the fractured location. Under higher stress at cryogenic temperature, the interaction of grain boundaries with massive TBs caused micro-voids to initiate more readily along the grain boundaries, resulting in premature failure.
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