The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy

0398843 - ÚFM 2014 RIV GB eng J - Journal Article
Otto, F. - Dlouhý, Antonín - Somsen, C. - Bei, H. - Eggeler, G. - George, E.P.
The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy.
Acta Materialia. Roč. 61, č. 15 (2013), s. 5743-5755. ISSN 1359-6454. E-ISSN 1873-2453
Institutional support: RVO:68081723
Keywords : high-entropy alloys * mechanical properties * deformation twinning * yield strength * temperature dependence
Subject RIV: JG - Metallurgy
Impact factor: 3.940, year: 2013

An equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (fcc) crystal structure, was produced by arc melting and drop casting. The drop-cast ingots were homogenized, cold rolled and recrystallized to obtain single-phase microstructures with three different grain sizes in the range 4-160 um. Quasi-static tensile tests at an engineering strain rate of 10(-3) s(-1) were then performed at temperatures between 77 and 1073 K. Yield strength, ultimate tensile strength and elongation to fracture all increased with decreasing temperature. During the initial stages of plasticity (up to similar to 2% strain), deformation occurs by planar dislocation glide on the normal fcc slip system, {1 1 1} < 1 1 0 >, at all the temperatures and grain sizes investigated. At later stages (similar to 20% strain), nanoscale deformation twins were observed after interrupted tests at 77 K. Related work hardening prevents the early onset of necking instability and is a reason for the enhanced ductility observed at 77 K. Since strong temperature dependencies of yield strength are also seen in binary fcc solid solution alloys, it may be an inherent solute effect, which needs further study.
Permanent Link: http://hdl.handle.net/11104/0226232