Stress-induced martensite variant reorientation in magnetic shape memory Ni–Mn–Gasingle crystal studied by neutron diffraction

Abstract

Stress-induced martensite variant reorientation in magnetic shape memory Ni–Mn–Gasingle crystal was studied in situ by the neutron diffraction technique. Principles ofdetermination of individual tetragonal martensitic variants in shape memory alloys areexplained. Using neutron diffraction we show that the macroscopic strain originates solelyfrom the martensite structure reorientation or variant redistribution. Neutron diffractionalso reveals that the reorientation of martensite is not fully completed even at a stressvalue of 25 MPa, which is about 20 times larger than the mean stress needed forreorientation. Only one twinning system is active during the reorientation process.