Characteristics of the Cold-Rolled Multi-Phase Cr30Fe30Ni15Co10Cu10Ti5 High-Entropy Alloy

Microstructure and mechanical behavior of a non-equiatomic Cr30Fe30Ni15Co10Cu10Ti5 high-entropy alloy were investigated during cold rolling. The alloy was cast by vacuum arc melting and after homogenization, it was hot rolled and solution annealed. The as-cast microstructure consisted of two face-centered cubic (FCC1: Ni-rich, FCC2: Cu-rich) and a hard Cr-rich sigma phases. The dendritic structure disappeared after solution annealing and the sigma phase partially transformed to a softer phase with a body-centered cubic (BCC) structure. The addressed thermomechanical process was found to result in favorable microstructural characteristics, which provided the possibility of subsequent heavy cold rolling up to 85% thickness reduction. Results indicated that while no phase transformation was detected during the cold rolling, the plastic deformation followed the dislocation slip mechanism at the early stages. The formation of mechanical twinning and shear bands were also identified as the main plastic deformation mechanisms at the higher levels of cold rolling in FCC1. In addition, grain refinement by dynamic recrystallization mechanism was observed in the BCC phase. However, the grain size of the Cu-rich phase was refined to < 500 nm after just a 25% thickness reduction. Although a small number of interfacial and intergranular cracks were initiated in some of the sigma phase particles, a good material flow was observed around this hard phase. The results also showed that applying 85% cold rolling lead to a significant increase in ultimate tensile strength (UTS) of the material to 1794 MPa. However, the optimum combination of UTS and elongation (1267 MPa and 31%, respectively) was achieved after thickness reduction of 40%.

Automated summary

This study investigates the microstructure and mechanical behavior of a non-equiatomic high-entropy alloy during cold rolling. The results show that no phase transformation occurs during cold rolling, and plastic deformation follows the dislocation slip mechanism at the early stages. Mechanical twinning and shear band formation are identified as the main plastic deformation mechanisms at higher levels of cold rolling.