Cooperative effect of monoclinic distortion and sinusoidal modulation in the martensitic structure of Ni2FeGa

The structural features of the “5M” martensitic phase in Ni2FeGa alloys have been determined by electron diffraction using the multi-slice least-squares (MSLS) method. The results demonstrate that the “5M” phase contains an evident cooperative effect of monoclinic distortion and sinusoidal modulation along the [110]c   direction. Theoretical simulations based on our refined data suggest that the “5M” martensitic phase observed in Ni–Fe–Ga and Ni–Mn–Ga has visible common behaviors in both stacking sequence and local structural distortion. Considering the cooperative effect of monoclinic distortion and sinusoidal modulation, we demonstrate that the “7M” martensitic phase could adopt two equivalent structural phases corresponding with the stacking sequences of (43−)2 and (52−)2, respectively.

The structural model of the “5M” Ni2FeGa martensite viewed along the [001]c (i.e. [010]m) zone axis, demonstrating the cooperative effect of monoclinic distortion and sinusoidal modulation along the [110]c direction.Figure optionsDownload as PowerPoint slide