Constant Plane Shift Model: Structure analysis of martensitic phases in Ni50Mn27Ga22Fe1 beyond non-modulated building blocks


New method to obtain different martensitic phases in Ni-Mn-Ga-Fe alloy with simplified variant microstructures allows us to analyze the crystal structure of NM, 14M, and 10M martensites in greater detail. We found that the short crystallographic axes of different martensites at the same temperature have different lengths which suggests that the equilibrium NM structure building blocks cannot be used to build the crystal structures of 14M and 10M martensites. As a replacement for the NM building block model we introduce a constant plane shift model with identical shifting values of the nearest planes (110) along [ ] or [ ]. The work demonstrates that the value of plane shifting differs dramatically between martensites in agreement with ab initio calculations. The application of the constant plane shift and hard sphere models in modulated lattices for atomic-level twinning considerations will be discussed.