Effect of rolling reduction on the microstructure, texture, and mechanical behavior of AZ91 alloy

Abstract

In this study, the effect of rolling reduction on the microstructure, crystallographic texture, and mechanical properties of the AZ91 alloy is studied. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and tensile and hardness tests were used. The homogenization process significantly increased the grain size of the as-cast sample. The results showed that {101¯2}⟨101¯1⟩ extension twinning during rolling leads to rotation of {0001}∥RD initial orientation toward {0001}‖ND basal texture. During asymmetric hot rolling up to 15%, the intensity of {0002} basal texture increased to 10 multiples of random distribution. After 15% deformation, the average grain size decreased due to the occurrence of dynamic recrystallization. It was found that by increasing the rolling reduction up to 15%, the hardness and tensile strength greatly increased owing to an increase in the fraction of twins and the intensity of basal texture. The occurrence of the CDRX mechanism and the formation of strong basal texture resulted in an excellent combination of strength and ductility for the 15% rolled sample. The as-homogenized and 8% rolled samples had the maximum and minimum inhomogeneity factor (IF), respectively. The fracture surfaces indicated that the mixture of ductile and brittle fracture is the main failure mode.