Microstructure, mechanical properties, and strain rate sensitivity of vacuum arc melted CoCrNi medium entropy alloy

Vacuum arc melting is a prevalent and low-cost technique to synthesize several metals and alloys. This study reports the microstructure, mechanical properties, and high strain rate testing of vacuum arc melted CoCrNi Medium Entropy Alloy (MEA). CoCrNi is a popular MEA owing to its better combination of strength and ductility, and the alloy also exhibits superior fatigue properties to the well-known first-generation CoCrFeMnNi high entropy or Cantor alloy. The CoCrNi MEA is found to be a single-phase face-centered cubic (fcc) solid solution and microstructural investigation revealed near-equiaxed coarse grains. Since strain hardening is an important mechanism for strengthening of CoCrNi at higher strains, the high strain rate tests are performed at strain rates of 103, 203, and 303 S-1. The strain hardening effect is dominant at higher strain rates, and a positive strain rate sensitivity of 0.256 ± 0.03 is observed.