High Critical Stress for Martensitic Transformation in 〈110〉 Oriented Single Crystal Cu-Al-Mn Superelastic Alloys with High Mn Content

The stress-induced martensitic transformation and superelasticity at room temperature were investigated by tensile tests on a series of single crystal Cu-17Al-xMn (x = 11.4, 12, 13, and 14 at%) shape memory alloys with a 〈110〉 orientation, aiming to increase the critical stress for martensitic transformation without plastic deformation. As the Mn content increased, the martensitic transformation temperatures decreased, and the critical stress for martensitic transformation increased from 180 MPa (11.4Mn) to 590 MPa (14Mn), exhibiting excellent superelasticity. For the 14Mn alloy, which showed a high critical stress, superelasticity was successfully obtained at temperatures ranging from 163 K to 293 K, and the temperature dependence of critical stress was revealed. Based on these data, the critical stress in Cu-17Al-Mn alloys with the 〈110〉 orientation was approximately formulated as functions of Mn content and testing temperature.