Temperature Dependence of Twinning Stress of Type I and Type II Twins in 10M Modulated Ni-Mn-Ga Martensite

We measure the temperature dependence of twinning stress in alloys with composition between Ni 50 Mn 28 Ga 22 and Ni 50 Mn 29 Ga 21 in the temperature range 288–334 K. For Type I twins, the twinning stress increases approximately linearly (0.04 MPa K −1 ) with decreasing temperature. For Type II twins, it is temperature independent and is about 0.2 MPa. The dependences are about the same in all alloys when presented as a function of the difference between the test temperature and the martensite transformation temperature.