Microstructure evolution and mechanical properties of 2196 Al-Li alloy in hot extrusion process

Abstract

Al-Li alloys are considered as promising materials for the aircraft and aerospace industries. As an effective way of producing complex profiles, the hot extrusion process has become more attractive. Here, isothermal extrusion of homogenized 2196 Al-Li alloys under the temperature of 703–783 K and extrusion speed of 0.1–1.0 mm/s was implemented. The microstructure and mechanical properties of extruded profiles under different processing conditions were evaluated. The results showed that the homogenization could eliminate the dendritic structure caused by casting and reduce segregation, creating a uniform element distribution. The insoluble intermediate particles composed of Al, Cu, and Fe were distributed on the grain boundaries with blocks and dots. After extrusion, the grains were flattened and elongated into thin fibers. With increasing extrusion temperature and speed, the misorientation of grains was increased, the degree of dynamic recovery and recrystallization were promoted, and the grain size was decreased. Increasing the extrusion speed properly is beneficial to grain refinement and dynamic recrystallization. The main texture components of the extruded profiles were Y, Cube textures with the orientations of <111>, <100>, and other {111} fibers. With the increasing temperature and speed, the texture types were changed from shear texture to recrystallization texture. The intensity of texture was decreased, while the texture diversity was increased. The hardness, tensile strength and yield strength of extruded profile were greatly enhanced, but the elongation was decreased. The tensile fracture morphology exhibited a large number of dimples, which was considered to be ductile fracture.