The Microstructure and Compression Behavior of Multi-Step Forging Ti-45Al-8Nb Alloy after Annealing at 1100 °C

Effects of annealing treatment on microstructure and the compressive properties of hot-worked Ti-45Al-8Nb-(W, B, Y) alloy were investigated. Microstructure of the extrusion plus multi-step forging pancake before and after heat treatment was analyzed by SEM and TEM, respectively. The annealing was conducted by holding samples at 1100°C for 2hrs, and followed by air cooling and furnace cooling. The mechanical properties were measured by Instron test machine. The microstructure evolution during compressive deformation was analyzed by TEM. The results showed that after the annealing the microstructure change could not be observed under SEM but can be observed under TEM. Many dislocation clusters were removed by heat treatment. The heat treated samples had similar compression behaviors with the pancake. TEM investigation showed that the numerous twin intersections occured in γ matrix during compression. The twin spaces tended to decrease as the deformation and the intersection increasing.