Static coarsening behavior of a pre-deformed Ti2AlNb-based alloy during heat treatment

Microstructure evolution, static coarsening mechanism and coarsening kinetics of a pre-deformed Ti2AlNb-based alloy during aging at 945 degrees C and 970 degrees C were investigated in this study. The corresponding microstructures were characterized by scanning electron microscopy and transmission electron microscopy. The results show that the pre-deformed alloy exhibited different morphologies aged at 945 degrees C and 970 degrees C. When the alloy was aged at 970 degrees C, the coarsening mechanism of the O precipitates was mainly controlled by the Ostwald ripening mechanism at first aging stage; after that, it was controlled by the boundary splitting mechanism and termination migration mechanism. Due to the difference in interface energy between the terminals and the long-axis direction of the O lath, diffusion process of solute atoms leads to the coarsening and fragmenting of O lath. The dimension of the O precipitates in the studied alloy continued to grow with the prolonged time during aging at 945 degrees C or 970 degrees C while the coarsening rate decreased. The static coarsening kinetic of the studied alloy was established in term of the modified Lifshitz-Slyozov-Wagner (LSW) theory. Static coarsening behavior of the predeformed alloy was mainly controlled by bulk diffusion at 945 degrees C and interfacial diffusion at 970 degrees C, respectively.