The effect of volume per cent of phase on the high temperature tensile deformation of two-phase TiMn alloys

Abstract

Abstract The high temperature (973 K) tensile deformation behavior of α, β and α-β TiMn alloys was studied as a function of volume per cent of the component phases and strain rate (2.6 × 10−2 − 10−4 s−1). Marked yield drops and strain softening were observed in the β phase, and the extent of drop increased with strain rate. Experiments indicated that the yield drop was not due to the declustering phenomenon. The yield drop was attributed to a sudden increase in the mobile dislocation density, and the apparent strain softening was attributed to the process of dynamic recovery. The flow stresses of the α-β alloys did not vary linearly with the volume per cent of β and did not follow the rule of mixture law based on constant stress or constant strain. The extent of deviation from linearity depended on the volume per cent of β and the strain rate. The strength of an α-β alloy with nearly equal volume per cents of the phases was found to be significantly lower than expected. This was attributed to the interface-sliding phenomenon in this alloy. Yield drops were also observed in α-β alloys, and the extent of yield drop and the apparent strain softening increased with increase in β content and strain rate. The finite element method was used to show that the local stresses in the β phase reach the critical flow stress required to cause the yield drop even though the overall applied stress in α-β alloys is much lower than this stress, resulting in flow stress drops in α-β alloys.