Flow Stress Behavior and Deformation Characteristics of Ti-22Al-25Nb Alloys at Elevated Temperature

摘要

The characteristics of deformation of an orthorhombic phase based alloy, Ti-22Al-25Nb (at%), have been studied by hot compression tests in the temperature range of 940-1150℃ with the strain rates of 0.01s~(-1) and 0.1s~(-1). A flow curves typically controlled by dynamic recovery were observed in the temperature range of 1090-1150℃ for the strain rate of 0.01s~(-1), while discontinuous yield phenomena was found for the strain rate of 0.1s~(-1). The dynamic recovery can be identified by the microstructure characteristics of the deformation specimens. At 1060℃, the temperature of beta transus, the flow curves and microstructure exhibited the same deformation charateristics as that above the beta transus. At the subtransus temperature, a long period of flow softening followed by the steady-state flow can be observed. During the hot deformation, the hard phases α_2 and O elongated, subboundary produced followed by cusp formation in the elongated α_2 and O phases, the equiaxed morphology phases occurred by B2 phase penetrating along the subboundaries. The softening mechanism was discussed.