Microstructure and properties of the near-β isothermally forged Ti₂AlNb based alloy

The microstructure evolution and mechanical property of Ti-22Al-25Nb (at%) alloy after near-β isothermal forging and heat treatment were studied. The results indicate that the duplex microstructure, which is consisted of a small amount of equiaxed α₂ particles and B2 matrix (containing fine lath O) appears after near-β isothermal forging and then air cooling. And this kind of duplex microstructure still exists after 960°C solution treatment with water cooling and then aging. However, when the alloy is treated at 940°C followed by water cooling and then aged, the tri-morphology microstructure, which is consisted of a small amount of equiaxed α₂ particles, coarse and fine lath O and B2 matrix, occurs. The strength of the alloy is reduced owing to the coarse lath O, while the ductility, endurance, fracture toughness and fatigue behavior are all improved which is of better matching than the duplex microstructure.