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Korean Journal of Metals and Materials > Volume 55(10); 2017 > Article
Korean Journal of Metals and Materials 2017;55(10): 732-738. doi: https://doi.org/10.3365/KJMM.2017.55.10.732
CoCrFeMnNi 고엔트로피합금 주조재의 미세조직 및 기계적 특성
강민주, 원종우, 임가람, 박상협, 서성문, 나영상
한국기계연구원 부설 재료연구소
Microstructure and Mechanical Properties of As-cast CoCrFeMnNi High Entropy Alloy
Minju Kang, Jong Woo Won, Ka Ram Lim, Sang Hyeop Park, Seong Moon Seo, Young Sang Na
Korea Institute of Materials Science, Gyeongnam 51508, Republic of Korea
Correspondence  Young Sang Na ,Tel: +82-55-280-3377, Email: nys1664@kims.re.kr
Received: 23 May 2017;  Accepted: 4 June 2017.  Published online: 28 September 2017.
ABSTRACT
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.
Keywords: high entropy alloy, mechanical property, microstructure, twinning
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