Effects of Aging Treatment on Microstructure Evolution and Mechanical Properties of Ti-6Al-3Nb-2Zr-Mo Alloy

In order to understand the influence of the different aging parameters on the microstructure and mechanical properties of Ti6Al-3Nb-2Zr-Mo (Ti6321) alloy, the microstructures and mechanical properties under different aging parameters (temperatures ranging from 500 degrees C to 650 degrees C, 3 - 24 h) were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical properties tests. The results reveal that the secondary alpha phase (alpha(s)) is more sensitive to the aging parameters than the primary alpha phase (alpha(p)). Moreover, the thickness of alpha(s) phase is positively correlated with aging temperature or aging time. As the aging temperature and aging time increase, the segregation of Ti and Al elements in the beta transformation phase (beta(t)) becomes obvious, and the alpha(s) phase changes from fine needle-like to long rod-like. When the alloy is aged at 600 degrees C for 12 h, the alloy shows good comprehensive mechanical performance. The tensile strength, yield strength, and elongation are 907 MPa, 796 MPa, and 16%, respectively, and the impact energy is 55 J.