Effect of heat treatment on transformation behavior of Ti-Ni-V shape memory alloy

Effects of annealing and aging processes on the transformation behaviors of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of differential scanning calorimetry (DSC). The A -> R/R -> A (A - parent phase, R - R phase) type one-stage reversible transformation occurs in 350-400 degrees C annealed alloy, the A -> R -> M/M R -> A (M - martensite) type two-stage transformation occurs in 450-500 degrees C annealed alloy, the A -> M/M -> A type transformation occurs in 550 degrees C annealed alloy, and A -> M/M -> A type transformation occurs in the alloy annealed at above 600 degrees C upon cooling/heating. The transformation type of 300 degrees C aged alloy is A -> R/R -> A, and that of 500 degrees C aged alloy is A -> R -> M/M -> A. while that of 400 degrees C aged alloy changes from A -> R/R -> A to A -> R -> M/M -> R -> A with increasing aging time. The effects of annealing and aging processes on R and M transformation temperatures and temperature hysteresis are given. The influence of annealing and aging temperature on transformation behaviors is stronger than that of annealing and aging time. (C) 2011 Elsevier B.V. All rights reserved.