Twin-based martensite stabilizing and improving the shape memory response of near equiatomic NiTi alloy through multi-axial forging

Abstract

In the present study, a high cumulative true strain (∼4.5) was applied on a near equiatomic NiTi shape memory alloy through multi-axial forging in the course of “isothermal” and “continuous cooling” regimes. It was found that the processed sample under decreasing temperature condition (from 900 °C to 660 °C) represented a full shape memory response without any residual strain. This behavior was discussed considering the effects of the compound twins on stabilizing the pre-existed martensite structure and favoring the detwinning stage compared with type I and type II deformation twins.

Keywords

• Shape memory materials
• Multiaxial forging
• Twin-based martensite
• Phase transformation
• Thermomechanical processing