Magnetic shape memory in Ni₂MnGa as influenced by applied stress

The authors report on the stress-strain and strain-temperature behaviors of a Ni2 MnGa alloy. Depending on the applied stress during cooling from austenite, different levels of transformation strain were observed culminating in the formation of a single variant of martensite and transformation strain of 4%. The results underscore an optimum stress level that maximizes shape memory strains. At higher stress levels, plasticity curtails the level of transformation strain and the concomitant magnetic shape memory strains. Similarly, the results uncover an optimum bias stress to maximize magnetic induced shape memory, producing strains exceeding 5% with reversible strains of 3%.