Influence of processing on microstructures of Ti-44Al-11Nb alloy

The cyclic and static oxidation behavior in the processing of Ti-44Al-11Nb alloy has been studied at 900, 950, and 1000 °C in air for a period of up to 168 hours (or a week). A recreation of diffusion paths for the oxide to penetrate into the base metal during every cycle results in the lower oxidation rates during cyclic mode compared to static mode. An extended period of heating time allows for the coarsening of the structure for both forms of alloys: polycrystalline and directionally solidified crystals. Coarsening and phase transformation in the heating period involves large amounts of dislocation activities in the lamellar structure as well as at the interface of lamellar structure and islands of γ.