EVOLUTION OF THE MICROSTRUCTURE OF AS-ROLLED Ti-43Al-9V-Y ALLOY WITH DIFFERENT HEAT TREATMENTS

The as-rolled Ti-43Al-9V-Y alloy sheet material investigated had a starting microstructure consisting of equiaxed gamma grains with a small volume fraction of B2 phase mainly located in gamma grain boundaries. As-rolled samples were heat treated at different temperatures ranging from 1200 degrees C up to 1320 degrees C. The hold time at these temperatures was 30 minutes. After different heat treatment, the equiaxed gamma grain size of the sheet does not increase dramatically but precipitation of B2 phase lamellas in equiaxed gamma grains is observed upon furnace cooling. Furthermore, after heat treatment at 1280 degrees C, gamma equiaxed grains were refined because the content of B2 laths formed in gamma equiaxed grains increased significantly. Microstructure of Ti-43Al-9V-Y alloy sheet transferred from gamma+B2 phase microstructure to DP microstructure after heat treatment of 1300 degrees C /30min. And after heat treatment at 1320 degrees C, many gamma equiaxed grains had been also changed into alpha 2/gamma/B2 lamellar structure, and the content of B2 phase of like-network shape increased.