Volume 8 Issue 1
Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling
Margarita Klimova, Nikita Stepanov, Dmitry Shaysultanov, Ruslan Chernichenko, Nikita Yurchenko, Vladimir Sanin and Sergey Zherebtsov
1Laboratory of Bulk Nanostructured Materials, Belgorod State University, Belgorod 308015, Russia
2Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Moscow 142432, Russian
*Author to whom correspondence should be addressed.
Abstract
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 (<40%), while grain (twin) boundary strengthening prevailed at higher strains.
Keywords:high-entropy alloys; microstructure evolution; twinning; mechanical properties; strengthening mechanisms