Elastic properties of Ni50Mn27Ga22Fe1 10M martensite with incommensurate lattice modulation

We present an elastic matrix for 10M Ni-Mn-Ga-Fe martensite with incommensurate (IC) lattice modulation and immovable twin boundaries (TBs). The modulation vector q I C = 0.4136 · q 110 for the investigated IC state is located between the values for the commensurate (C) state, q C = 0.4 · q 110 , and the maximum value for IC 10M structures reported in various studies q I C m a x = ( 3 / 7 ) q 110 = 0.4286 · q 110 . The elastic matrix obtained for the IC modulated lattice differs in certain components, especially those related to shear in a/b system, as well as the corresponding Young’s moduli, compared to the values reported for martensite with C modulation. This study presents experimental evidence of internal stability in IC modulated structure, subjected to stresses that significantly exceed the a/b twinning stress (TS) observed in C structures. This study examines the observed differences in the small stress response of C and IC lattices, emphasising the roles of highly mobile a/b TBs and lattice instability near TBs in the C case.