CoCrFeMnNi 고엔트로피합금 주조재의 미세조직 및 기계적 특성

• Published in: 대한금속·재료학회지, 55(10) Vol. 55; no. 10; pp. 732 - 739
• Main Authors: 강민주, Minju Kang, 원종우, Jong Woo Won, 임가람, Ka Ram Lim, 박상협, Sang Hyeop Park, 서성문, Seong Moon Seo, 나영상, Young Sang Na
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.10.2017; 대한금속·재료학회
• Subjects: high entropy alloy; mechanical property; microstructure; twinning; 재료공학
• ISSN: 1738-8228; 2288-8241
• DOI: 10.3365/KJMM.2017.55.10.732

In this study, we made large-scale ingots of CoCrFeMnNi high entropy alloy by vacuum induction melting. The as-cast CoCrFeMnNi high entropy alloy contained a high proportion of columnar structures with a few equiaxed grains, and showed single phase fcc solid solutions without macro segregation and low interstitial levels. The tensile properties along the three different loading directions were investigated at low-temperature and room temperature. A decrease in temperature led to an increase in yield and tensile strengths. The increase in anisotropy due to the columnar structure was negligible. Unlike wrought CoCrFeMnNi high entropy alloys, twins were actively formed in the specimen deformed at room temperature. Mechanical twinning was found to be a result of the coarse grain size, over 500 μm, of the as-cast CoCrFeMnNi high entropy alloy, which effectively reduced the critical stress for twinning. Charpy impact tests were also conducted, and the absorbed energy of the CoCrFeMnNi high entropy alloy showed no dependence on the temperature or loading directions. The results of this study provide an understanding of pilot-scale high entropy alloy castings, and are expected to be utilized as basic properties for manufacturing large-scale high entropy alloy castings, which are effective in severe environments. (Received May 23, 2017; Accepted June 4, 2017)