Investigation on intermartensitic transformation in Ni-Mn-Ga alloy

A complete thermally induced intermartensitic transformation has already be en observed in a single crystalline Ni-52 Mn24Ga24 sample with martensitic transformation temperature (M-s) near room temperature. As constrast with t he single crystalline sample, polycrystalline samples, even those annealed ones, did not show this intermartensitic transformation. The experimental r esults indicates that the intermartensitic transformation can be suppressed by mechanically grinding the single crystalline sample to smaller sizes. T his has been attributed to the internal stress and serious Lattice distorti on caused by the grinding process. The intermartensitic transformation migh t be suppressed by the elastic energy stored in distorted Lattice. As the e vidence,grinding the sample to 50 mum,the martensitic transformation was ev en disappeared in the present measurements. Based on this point,the uncompl eted intermartensitic transformation observed in the previous works can be explained.