The transformation sequence is suggested as P param ⟶T param ⟶ T ferrom with reverse reactions in respective order. In Ni 53.7 Mn 26.4 Ga 19.9 the magnetic transition was clearly below the parent to martensite phase transformation and did not have hysteresis.

The transformation enthalpies of melting, solidification and martensitic/reverse reactions were determined.

The liquidus, solidus and L2 1 ⟶B2’ temperatures were detected for the alloys. The transformation behavior of Ni 50.5 Mn 30.4 Ga 19.1 and Ni 53.7 Mn 26.4 Ga 19.9 was studied with ac magnetic susceptibility, differential scanning calorimetry, in-situ optical microscopy and X-ray diffractometry. The present study is instructive for understanding the phase transition between coexisting multiple martensites under external fields and may shed light on the design of novel functional properties based on such phase transitions. The magnetic-field-induced transformation from 7M martensite to NM martensite at 140 K where 5M + 7M + NM multiple martensites coexist before applying the magnetic field was observed by in situ neutron diffraction experiments. The transition between coexisting multiple martensites with monoclinic and tetragonal structures during cooling was observed in the Ni51.5Mn26.5Ga22 (x = 5.5) alloy, and it was found that 5M + 7M multiple martensites coexist from 300 K to 160 K and that 5M + 7M + NM multiple martensites coexist between 150 K and 100 K. A phase diagram of this Ni57−xMn21+xGa22 alloy system was constructed. %) magnetic shape memory alloys was performed by a temperature-dependent synchrotron X-ray diffraction technique and transmission electron microscopy. All these findings were supported by scattering electron microscope (SEM) and metal microscopy studies.Ī comprehensive study of the crystal structure and phase transition as a function of temperature and composition in Ni57−xMn21+xGa22 (x = 0, 2, 4, 5.5, 7, 8) (at. In one of them, the first martensitic transformation leads to a martensitic phase having a commensurate modulated lattice characterized by a periodic stacking sequence of ten B2. A two-step thermally induced martensitic transformation during cooling and one-step reverse transformation during heating have been found in both alloys, although involving different modulated martensitic phases in each of the alloys. In the other alloy, the transformation sequence observed on cooling is from the parent phase to an eight-layered modulated martensite followed by a second transformation to a martensite having a tetragonal lattice ( c / a > 1 ) without modulation.The martensitic transformation sequence in two single crystalline Ni-Mn-Ga alloys with a martensite start temperature (Ms) of about 400 K has been investigated using dynamic mechanical analysis, calorimetry, dilatometry, three-point bending tests, and transmission electron microscopy. On further cooling, a second transformation to a modulated martensite with a periodicity of seven planes has been observed. In one of them, the first martensitic transformation leads to a martensitic phase having a commensurate modulated lattice characterized by a periodic stacking sequence of ten P planes along the 〈 110 〉 P direction. The martensitic transformation sequence in two single crystalline Ni-Mn-Ga alloys with a martensite start temperature ( M s ) of about 400 K has been investigated using dynamic mechanical analysis, calorimetry, dilatometry, three-point bending tests, and transmission electron microscopy.

Sequence of transformations