Studies on ordering temperature and martensite stabilization in Ni55Mn20−xGa25+x alloys

Effect of process parameters on non-modulated Ni-Mn-Ga alloy manufactured using powder bed fusion

“…Compared to the phase transformation temperatures of the heat-treated atomized powder, the phase transformation in the PBF samples occurred at temperatures that are approximately 10-20 degrees higher. As it is known [56][57][58][59], the atomic ordering of the L2 1 structure affects the properties of the structure since the ordering of the parent phase is inherited during the martensitic transformation. The effect of increased ordering can be typically observed by the elevated Curie and martensitic transformation temperatures [56][57][58][59].…”

“…As it is known [56][57][58][59], the atomic ordering of the L2 1 structure affects the properties of the structure since the ordering of the parent phase is inherited during the martensitic transformation. The effect of increased ordering can be typically observed by the elevated Curie and martensitic transformation temperatures [56][57][58][59]. As the heat-treatment procedure for the PBF parts included both homogenization at 1000°C and ordering treatment at 800°C, it is likely that the PBF parts have a fully homogenized and ordered structure.…”

Recent Development in Magnetic Shape Memory Alloys

“…Figure 4 shows the differences in the diffraction conditions and the signal recording between polycrystalline and single crystal samples. The atomic interplanar spacings can be determined by knowing the measurement angles and employing the Bragg's law [54][55][56][57]. For both single crystal and powder neutron diffraction, and by making the corresponding mathematical corrections to the recorded intensity profile at the detector, it is possible to refine the structure and atomic ordering from fittings to that intensity profile using structure refinement programs such as, e.g., Fullprof [58].…”

Estimation of driving force for martensitic transformation in (Ni52.5Mn23.5Ga24)100−xCox alloys

“…Several studies have suggested that the starting temperature of martensite transformation (M s ) is a function of the valence electron concentration (e/a) and/or the volume of the unit cell of the alloy [8][9][10]. Heat treatment also alters the M s via the ordering of the L2 1 phase in a small scale [11,12]. These conclusions have also been confirmed in Ni-Fe-Ga alloys and the Ge-, Co-or Fe-added Ni-Mn-Ga alloys [13][14][15].…”