Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling

• Published in: Materials 2017-12, Vol.11 (1), p.53
• Main Authors: Klimova, Margarita, Stepanov, Nikita, Shaysultanov, Dmitry, Chernichenko, Ruslan, Yurchenko, Nikita, Sanin, Vladimir, Zherebtsov, Sergey
• Format: Article
• Language: English
• Subjects: Banding; Chemical synthesis; Cold rolling; Deformation; Dislocation density; Edge dislocations; Elongation; Evolution; High entropy alloys; Manganese; Mechanical properties; Microstructure; Nickel; Self propagating high temperature synthesis; Stacking fault energy; Twinning; Yield strength; Yield stress
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11010053

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20-23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (