Generation mechanism of oxygen rich α layer in TA15 and TA2 titanium alloy

The oxygen-rich α layers in TA2 and TA15 alloy after various heat treatments were studied. The forming thermodynamics and kinetics of oxygen-rich α layer were discussed. Optical microscope was used to observe α layer and measure its thickness. The results show that both heat treatment temperatures and holding times control the forming of oxygen-rich α layer, and temperature is main factor. The kinetics curves of α layer controlled by oxygen diffusion show parabolic shape. The thermal activation energy calculated results of α layer are 146.48 kJ/mol of TA15 alloy and 59.97 kJ/mol for TA2 alloy. The alloy type and alloying elements, delaying diffusion of oxygen in the α phase, is the main reason of the difference between these two alloys. A three-dimensional curve of TA15 alloy was created to show the layer thickness under different conditions of exposure temperature and time.