Effects of Cold-Rolling and Subsequent Annealing on Microstructure and Mechanical Properties of (CrCoNi)97Al1.5Ti1.5 Medium-Entropy Alloy

In this study, the (CrCoNi)(97)Al1.5Ti1.5 medium-entropy alloy (MEA) is prepared and subjected to cold-rolling and annealing. The phase and microstructure are characterized by using X-ray diffraction (XRD), backscattered electron imaging (BSEI), electron backscattered diffraction (EBSD), and transmission Kikuchi diffraction (TKD). Microhardness and tensile properties of the deformed and annealed samples are measured. The results show that a large amount of lamellar dislocation substructures (LDS) is formed during cold-rolling up to 50% reduction. After a 50% rolling reduction and annealing at 600 degrees C for 1 h, the LDS inside the deformed grains does not change significantly. When the annealing temperature increases to 650 degrees C, a large amount of LDS begins to disappear and is replaced by recrystallized grains and high-density annealing twins. When the annealing temperature reaches 700 degrees C, a completely recrystallized structure is obtained. Cold-rolling deformation leads to a linear increase in the microhardness and tensile strength of MEA. The 50% reduction sample will harden again after short-time annealing at 600 degrees C while softening will occur after annealing at 650 degrees C or 700 degrees C. The deformation mechanisms and strengthening mechanisms are also discussed and analyzed.