Microstructure, texture, and mechanical properties of asymmetrically cold-rolled Ni1.5FeCrCu0.5 high-entropy alloy

Abstract

This study deals with the microstructural evolution, texture development, and mechanical properties of the cold-rolled and annealed Ni1.5FeCrCu0.5 high-entropy alloy (HEA). In addition to symmetric rolling (SR), asymmetric rolling (AR) was performed with different velocity ratios (VRs) between the working rolls. Electron backscatter diffraction (EBSD) measurements showed that the grain size of the annealed samples was drastically reduced by increasing the VR of the rolls and imposing shear strain. Moreover, annealing was associated with forming a high volume fraction of annealing twins. Recovery was accelerated by increased accumulated shear strain through the thickness of the ARed strips. The X-ray diffraction (XRD) method was employed to investigate the crystallographic texture in the processed high-entropy alloy. Macrotexture data revealed that the intensity of E {111} <110> and F {111} <112> shear texture components were remarkably higher in the ARed sheets. However, the intensities of S {123} <634> and Copper {112} <111> orientations were decreased in favor of the Brass {011} <211> component, indicating the pure-metal to alloy type texture transition in low stacking fault energy (SFE) materials. Compared to the homogenized sample, the Cube {001} <100> component was dramatically weakened by the annealing of the cold-rolled specimens. In terms of the mechanical properties, the pronounced grain refinement of the post-roll annealed strips enhanced the yield strength (YS) and ultimate tensile strength (UTS) from 332 to 503 in the homogenized condition to 625 and 709 MPa in the asymmetrically rolled (ARed) sample with a velocity ratio of 8. Finally, plastic anisotropy analysis demonstrated that the sheet drawability was gradually improved by increasing the velocity ratio due to the increased mean r-values and reduced planar anisotropy (Δr) values.