Analysis of microstructure and microtexture during grain growth in low stacking fault energy equiatomic CoCrFeMnNi high entropy and Ni–60 wt.%Co alloys

Abstract

The evolution of microstructure, texture and fraction of annealing twin boundaries is studied in Ni–60wt.%Co and equiatomic CoCrFeMnNi high entropy alloy (HEA) with similar low stacking fault energy (SFE). The two materials are cold-rolled to 90% reduction in thickness and subjected to different annealing treatments to achieve very similar average grain size. The twin boundary fraction in the two materials was found to be similar for the same average grain size. This indicated that twin boundary fraction depended on the final grain size. The two alloys revealed a strong brass type deformation texture typical of low SFE materials. However, the texture after grain growth in the two alloys was strikingly dissimilar. The Ni–Co alloy showed strong α-fiber (ND//〈110〉) components, namely, G ({110}〈011〉) and G/B ({110}〈115〉) due to the preferential growth of these components. In contrast, the microstructure of the HEA showed no preferential grain growth and texture components in HEA revealed only minor changes. These sharply different microstructure and texture formation mechanisms in the two alloys could be explained on the basis of sluggish diffusion in multicomponent HEA which greatly diminished grain boundary mobility and restricted preferential grain growth.