The effect of heating rate on microstructure and texture formation during annealing of heavily cold-rolled equiatomic CoCrFeMnNi high entropy alloy

Abstract

The effect of heating rate on the formation of microstructure and texture was investigated in a heavily cold-rolled and annealed equiatomic CoCrFeMnNi high entropy alloy. For this purpose, the alloy was 90% cold-rolled and annealed for 2 min (mins) and 60 min at temperatures ranging from 700 °C to 1000 °C using two different heating rates, namely high heating rate (HHR) of 10 °C/s and low heating rate (LHR) of 0.013 °C/s. The cold-rolled material developed a very fine deformation microstructure and strong brass type texture. The LHR treated materials consistently showed higher average grain size and wider grain size distributions as compared to those in their HHR treated counterparts. This could be attributed to the early activation of nucleation sites during LHR treatments. However, the annealing textures of the HHR and LHR treated materials were very similar, confirmed by the qualitative and quantitative texture analyses of the individual components and overall texture strength. The texture development could be adequately explained on the basis of absence of strong preferential orientation selection and preferential growth, which resulted from the more homogeneously deformed matrix and sluggish diffusion, respectively. The present results indicated that heating rate could significantly affect the average grain size and grain size distribution during annealing, but the annealing texture remained largely unaffected.