Deformation and microstructure of Ti-14Mo alloy in over aged state

Deformation and microstructure were investigated on Ti-14 mass%Mo alloy in over aged state using the duplex aging method. In the over aged state only hardness decreased in spite of no change in both size and composition of ω phase. Though the ω phase aged at 623 K for 1 × 10⁶ s had the maximum hardness and resulted in the brittle fracture through ω→β″ transformation, they became soft by over aging and transformed to α phase within the deformation band. The α particles in the band were sheared by {1011}_α twinning which direction was perpendicular to the band product. The twinning of α particles was regarded as a complementary deformation with volume change in the ω→α transformation. It was suggested that the occurrence of the band product consisted of β+α phases would not be directly connected with brittle fracture.