Evolution of microstructure and mechanical properties of asymmetrically rolled AA2219 alloy at different temperatures

Abstract

Asymmetric rolling of cast AA2219 alloy was carried out at −150°C (cryo-rolling), 340°C (warm rolling), and 550°C (hot rolling). Microstructure and mechanical property analysis of the rolled samples were carried out at room temperature. From microstructural observations, the average grain size decreases with increasing rolling percentage at a given temperature. However, the grain size distribution is more heterogeneous at lower than at higher rolling temperatures. The mechanical properties of the rolled samples are evaluated using indentation hardness techniques. The hardness increases with increasing reduction percentage for the cryo-rolled sample. However, the hardness decreases with increasing reduction percentage for the warm and hot-rolled samples, which can be attributed to precipitate overaging. To understand the microstructural evolution, FEM modelling was performed using ABAQUS. The FEM modelling showed that the von Mises’ residual stress accumulation was greater in the cryo-rolled sample, followed by the warm and hot-rolled samples. The above trend holds for the accumulated dislocation density in the sample during rolling. The high dislocation density in the cryo-rolled sample results in a higher average hardness value than in the warm and hot-rolled samples at 50% and 75% TRP (Thickness reduction percentage). Further, the extent of grain refinement is greater in the cryo-rolled samples than in the warm and hot-rolled samples, due to the suppression of dynamic recovery during rolling.