Texture evolution and microstructural thermal stability of as-extruded AA2099 during hot deformation

Abstract

Two thermal-mechanical regimes were selected to investigate the recrystallization process of an as-extruded AA2099 alloy. Specimens were deformed to strains of 0.4, 0.7 and 0.9 at 520°C and strain rates of 0.001s−1 and 0.1s−1, respectively. Electron backscatter diffraction (EBSD) and electron channeling contrast (ECC) imaging were performed for all specimens to characterize their textures and microstructures. The texture evolution is reflected by variation of deviation angle between <111> and extrusion directions, which appears to progressively approach ~35° (<110>//ED) due to lattice rotation in both regimes before ε=0.7. The reconstruction maps indicate that the nucleation of recrystallization is related to strain incompatibility near grain boundaries. The textures of specimens deformed to strain of 0.9 exhibit significant difference between the two regimes, i.e the <110>//ED fiber texture is comparatively weakened by recrystallization nuclei growth at the lower strain rate (0.001s−1). ECC images for specimen deformed at 0.001s−1 reveal significant differences in size and volume fraction of Al3Zr particles between recrystallized and unrecrystallized regions, suggesting remarkable influence of boundary migration on the thermal stability of Al3Zr particles.