Kinetics, mechanism, and pathway of reorientation of multi-variants in Ni-Mn-Ga shape memory alloys under continuous compressive stress: Phase-field simulation

The kinetics and mechanism of reorientation of martensitic variants as well as the evolutional pathway under the continuous compressive stress along different directions in Ni-Mn-Ga alloys have been investigated by using phase-field method. The simulated results revealed that the final structures and the pathway of evolution were determined by the stress-applied direction: two variants, single variant and the complete parent corresponding to the [100], [110], and [111] directions, respectively. The related kinetics and the mechanism of the structural conversion and the phase transition will be proposed to explain the inner physical nature. The twinning or detwinning stress was calculated for different directions and also discussed from the effect of the interfacial dynamic factor and the shear modulus, which was close to the experimental measurements. The pseudo-elasticity related to the structural conversion as well as phase transition was also investigated. The reversibility of structural evolution between two variants and among three variants was observed and discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4765011]