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 alpha/beta and beta solution treatment were introduced to study the relationship between microstructural characteristics and mechanical properties. Large quantities of strip shape primary alpha phases form during the alpha/beta solution treatment, which not only increase the stability of beta matrix, but also suppress the growth of secondary alpha phase during subsequent aging. In alpha/beta solution plus aging condition, the alloy is composed of a mixture of primary alpha phase, secondary alpha phase and beta 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 alpha 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 beta grains. When the alloy is under beta solution plus aging condition, many secondary alpha phases with acicular shape around 80-200 nm in width precipitate in p 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 alpha/beta solution treatment conditions to a mixture of intercrystalline and transcrystalline fracture at the beta solution treatment condition. (C) 2014 Elsevier B.V. All rights reserved.