Tuning mechanical behavior of an FCC high entropy alloy: Insights from roll deformation and texture

Abstract

Severe plastic deformation (SPD) is introduced as a significant approach in designing and tailoring the mechanical characteristics of high entropy alloys (HEAs). This research focuses on investigating the microstructure evolution, deformation mechanisms, and their influence on texture components and mechanical behavior in a single solid solution Ni1.5FeCrCu0.5 HEA subjected to cold rolling. For this purpose, microstructure evolution and texture expansion were studied in 25, 45, 65, and 85 % thickness reductions using electron backscatter diffraction (EBSD) as well as transmission electron microscopy (TEM). The finding illustrates that alongside dislocation density, deformation twins and shear bands increase with higher strain; in particular, nanotwins with a thickness of approximately 50 nm were observed in the 85 % cold rolled (85 % CR) alloy. Bulk texture analysis indicates that the presence of shear bands and twins leads to the Goss {110}<001> and Brass {110}<112> texture orientations in the cold-rolled samples, which is ascribed to the low SFE of the alloy. With increased strain, the alloy's hardness and yield strength increased from ∼150 Hv and ∼236 Mpa (As-cast sample) to ∼467 Hv and ∼1097 Mpa (85 % CR), respectively, while the elongation decreased by ∼66 %. By examining the alloy's strengthening mechanisms, it has been determined that increasing the dislocation density and the presence of twins are the two main strengthening mechanisms of the alloy.