Improving the temperature stability of superelastic stress of Cu-Al-Mn shape memory alloy in a wide temperature rang by torsion pre-deformation

摘要

To improve the temperature stability of shape memory alloys (SMAs) in wide temperature range, the torsion pre -deformation (TPD) treatment was used to realize the dual phases (austenite and martensite) control and reduce temperature dependence of superelastic stress in columnar-grained Cu-Al-Mn SMAs. Results show that residual martensite phase in the samples is distributed in a gradient across the cross section after TPD with the unit torsion angle (v') of 0.75-3.75 degrees /mm. Dual-phase structure after TPD can suppress temperature dependence of superelastic stress of SMAs while maintaining the superelasticity obviously under large strains. The change rate of stress-induced martensitic transformation stress with temperature (da/dT) of Cu-Al-Mn SMA after TPD (v'=0.75 degrees /mm) is 0.37 MPa/K over a wide range of temperature about 200 K, which is better than other re-ported Cu-Al-Mn SMAs and NiTi SMAs.