Prediction of Microstructure During High Temperature Forming of Ti-6Al-4V Alloy

摘要

A study has been made to investigate the high temperature deformation behavior of Ti-6Al-4V alloy and to predict the final microstructure under given forming conditions. Equiaxed microstructure of Ti-6Al-4V alloy was prepared as starting microstructures. By performing the compression tests at high temperatures (700-1100 deg C) and a wide range of strain rates (10~(-4) - 10~2/s), flow stress-strain curves obtained and various parameters such as strain rate sensitivity (m) and activation energy (Q) were obtained and used to established constitutive equations. When the specimens were deformed up to strain of 0.6, equiaxed microstructure did not show any significant changes in morphology, while the average a grain size was varied with variation of volume fraction at different temperatures and strain rates. Accordingly, constitutive equations were developed by use of internal state variables, and applied to predict the final microstructure after forming. Finally, the finite element analysis was performed considering the microstructural evolution during the hot deformation, and the grain size and the volume fraction of a phase of deformed body were predicted and compared with the experimental results through the actual forging process.