Influence of oxides on the cryogenic tensile properties of the laser aided additive manufactured CoCrNi medium entropy alloy. (1st July 2021)

• Record Type: Journal Article
• Authors: Weng, Fei; Chew, Youxiang; Zhu, Zhiguang; Sui, Shang; Tan, Chaolin; Yao, Xiling; Ng, Fern Lan; Ong, Wee Kit; Bi, Guijun
• Is Part Of: Composites. Number 216(2021)
• Publication Date: 2021-07-01
• Subjects: Medium entropy alloy -- Laser aided additive manufacturing -- Oxide -- Cryogenic properties -- Microstructure; Composite materials -- Periodicals; Materials science -- Periodicals; Composite materials; Periodicals; Electronic journals; 620.118
• DOI: 10.1016/j.compositesb.2021.108837
• Languages: English
• ISSNs: 1359-8368

Abstract

Abstract: 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. Graphical abstract: Image 1 Highlights: CoCrNi medium entropy alloys with different amount of oxides were fabricated by LAAM. The effect of oxides on the cryogenic tensile properties of CoCrNi MEA was investigated. Twin boundaries (TBs) were found distributed unevenly near the fracture position. Lower elongation was attributed to the uneven-distributed TBs and internal pores.