Microstructure evolution of the TiB2/Al composites fabricated by powder metallurgy during hot extrusion

Abstract

The microstructure evolution near the central axis during hot extrusion for the fine-grained TiB2/Al-Zn-Mg-Cu composites fabricated by powder metallurgy is studied by experimental observation at different locations in the remaining die. The significant increase of the fraction of ultrafine grains and texture evolution indicates the extensive dynamic recrystallization at the narrowest position of the die. The deformed grains are distinguished from the undeformed grains with the parameter of grain orientation spread (GOS). And the deformed grains are generally rotated around the extrusion direction. Additionally, the introduced submicron TiB2 particles have the potential to stimulate the dynamic recrystallization associated with progressively increased misorientation of subgrain boundaries, and even change the spatial distribution of the low angle grain boundaries. The preferential activation of {111} 〈1−10〉 system and non-octahedral (NOC) slip system {001} 〈110〉 contributes to the formation of strong deformation fiber texture according to the analysis of the Schmid factor. It is supposed that grain boundary sliding accommodated dislocation slip mechanism controls the microstructure evolution.