Effect of solutionizing temperature and cooling rate on phase morphology, recrystallization and texture evolution in a heat treated Ti-6Al-4Valloy having different types of microstructure

The effect of different solutionizing temperature and cooling rate on the extent of recovery, recrystallization and texture evolution in the alloy Ti-6Al-4V (Ti-64) has been investigated in different microstructural conditions. The hot rolled Ti-64 alloy was subjected to three different heat treatments in order to obtain three different microstructures, namely, lamellar (beta-treatment), and equiaxed and bimodal (alpha/beta-treatment). The heat treated alloys were characterized in terms of differences in phase fraction and phase dimension, the extent of recovery, recrystallization and texture evolution using SEM, EBSD, TEM, and XRD. The effect of heat treatment parameters on the volume fraction and grain size of primary alpha was more in bimodal mi-crostructure than that of the equiaxed microstructure. The width of transformed alpha laths increases with increasing soaking temperature. Additionally, the extent of recovery and recrystallization of primary alpha was higher in equiaxed microstructure than in bimodal microstructure. The higher solutionizing temperature caused the dislocations in primary alpha to arrange themselves into lower energy substructures, which ulti-mately lead to subgrain formation. In transformed alpha laths, dislocations were generated due to lattice strain induced during beta to alpha phase transformation. The rolling texture vanished gradually as the microstructure recovered and new recrystallized primary alpha grains grew. The newly formed recrystallized primary alpha grains and the majority of transformed alpha showed a moderate and strong prismatic texture respectively.(c) 2022 Elsevier B.V. All rights reserved.