Microstructure and mechanical properties of new high strength beta-titanium alloy Ti-1300

The influence of aging treatment on microstructural characteristics and mechanical properties of Ti-1300 alloy was investigated in this work, and both the α/β and β solution treatment were introduced to study the relationship between microstructural characteristics and mechanical properties. Large quantities of strip shape primary α phases form during the α/β solution treatment, which not only increase the stability of β matrix, but also suppress the growth of secondary α phase during subsequent aging. In α/β solution plus aging condition, the alloy is composed of a mixture of primary α phase, secondary α phase and β phase, which results in a high strength above 1350 Mpa with elongation over 13.5%. With the increasing of aging temperature, the strength decreases and the plasticity increases, the primary α phase is also remarkably coarser in width than that in length, and which rejects the moving of the dislocation and restrains the size of prior β grains. When the alloy is under β solution plus aging condition, many secondary α phases with acicular shape around 80-200 nm in width precipitate in β matrix, and the alloy exhibits superior strength around 1640 Mpa, but the elongation decreases to about 4.5%. Fractography analysis shows that fracture mechanism changes from a transcrystalline fracture at the α/β solution treatment conditions to a mixture of intercrystalline and transcrystalline fracture at the β solution treatment condition.