The way composition affects martensitic transformation temperatures of Ni–Mn–Ga Heusler alloys

Abstract

A systematic substitution of Ge, Si, C and Co for Ga in the non-stoichiometric Ni -Mn -Ga alloys was performed. The relationship between the compositions of different elements including Ni, Mn, Ga, Ge, Si, C, Co, In and martensitic transformation temperature (M s ) was studied in detail for the present alloys together with data collected from a variety of sources. It is found that M s is a sensitive parameter to the composition. The size factor and electron concentration are usually thought to be the way the composition influences M s in the Ni -Mn -Ga alloys. Here, analyzing by linear regression, the electron density maybe a most appropriate parameter to describe the way the composition influences M s when compared with size factor and electron concentration.

Intermartensitic transitions and phase stability in Ni50Mn50−Sn Heusler alloys

“…In such a case, the system tends to minimize the free energy by creating the distortions. The new Brillouin zone pattern corresponds to the new crystal structure, which is martensite [29,30]. The increase in the density of the valance electron number leads to a higher M s , and depending on the excess in the conduction electrons at the Fermi level, the 5M, 7M or L10 martensite structures form.…”

Fe and Co selective substitution in Ni2MnGa: Effect of magnetism on relative phase stability

“…Khan et al [62] specifically studied the effect of isoelectronic substitution of Ga by In in Ni 2 MnGa and concluded that the effect of Z on M s mainly arise from the change of unit cell volume which modifies the relative position of the Brillouin zone boundary and Fermi surfaces. The role of volume effects on the martensitic transition has been further studied via doping of Ni-Mn-Ga with several other elements and use of electron density to parametrize structural transition temperatures has been suggested [63,64]. The effect of magnetism on the martensitic transition, however, has been studied in less detail.…”

Site preference and elastic properties of Fe-, Co-, and Cu-doped Ni2MnGa shape memory alloys from first principles

“…19 Here, V cell is the volume of the unit cell and N is the number of atoms contained in the unit cell. On the other hand, the shear modulus C = 1 2 (C 11 − C 12 ) may also serve as the predictor of the composition-dependent T M .…”