Lightweight Shape Memory Alloys Research Articles

Effects of thermomechanical treatment on microstructure and shape memory effect of Ti–13V–3Al lightweight shape memory alloy

The effects of thermomechanical treatment on microstructure, mechanical properties and shape memory effect of Ti–13V–3Al alloy were investigated. A dual-phase structure which consists of α phase and α″ martensite phase forms after thermomechanical treatment. As annealing temperature increases, the amount of α phase decreases and its morphology changes. Stress plateau decreases when annealing temperature increases and elongation shows the opposite trend. Ti–13V–3Al alloy annealed at 700°C has the best comprehensive mechanical property. Recoverable strain first increases then decreases as annealing temperature increases. Ti–13V–3Al alloy annealed at 700°C for 0.5h displays a large fully recoverable strain of 7.5%. It is believed that small, uniformly distributed α phase benefits the shape memory effect. With the help of α phase, martensite variants become small. The variants are supposed to have a good mobility and that reduces the chance of introducing irrecoverable strain during tensile test. The microstructure evolution of Ti–13V–3Al alloy annealed at 700°C during deformation was investigated. When the pre-strain is less than 7.5%, the recoverable martensite reorientation process contributes to the deformation. When the pre-strain exceeds 7.5%, the crossover of martensite plates leads to the deterioration of shape memory effect.