Effects of solution time on microstructure and mechanical properties of Ti-22Al-24Nb alloy

In this research, the changing rules of billet forged Ti-22 Al-24 Nb alloy with various solution time were studied, and the mechanical properties of different microstructure were tested at the room temperature. The results indicate that the(α2+O+B2) three-phase microstructure with equiaxed grains was acquired by Ti-22 Al-24 Nb alloy billet forging, and the average size of the grains was about 300 μm. With the increase of solution time, the primary lath-shaped O phase began to dissolve, and then the equiaxial α2 phase started to dissolve, but the undissolved α2/O phase began to be equiaxial and grow. The grains of original B2 phase recrystallized and grew. After the 2 h solution treatment, the recrystallization of grains was completed basically and the average size of the grains was about 100 μm. After the 2.5 h solution treatment, the strength of the alloy decreased, and the plasticity increased. However, when the solution treatment increased to 3 h, the plasticity decreased but the strength increased. The optimal solution parameters of Ti-22 Al-24 Nb alloy were the holding time of 2 h, the solution temperature of 1 000 ?C, and water cooling. Excellent comprehensive mechanical properties can be accquired under these parameters. The tensile strength, the yield strength, the elasticity modulus, the elongation, and the section shrinkage were 950 MPa, 915 MPa, 90 GPa, 15.69% and 42.28%, respectively.