Fracture mechanism of a Ni-Mn-Ga ferromagnetic shape memory alloy single crystal

Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) have shown large magnetic-field-induced strains up to 10%. The fracture behavior of these materials under thermal and magnetic cycling has not been reported so far. An Ni-Mn-Ga single crystal exhibiting both thermal and magnetic shape memory effect was investigated in the present study. Coexistence of differently oriented martensite twinned variants and its effect on the magnetization and fracture mechanism were studied. Fracture behavior of this alloy was found to be strongly related to the martensitic transformation while the fracture surface was parallel to one of the {112} martensite twin planes. Different orientations of martensite variants were responsible for the formation of the crack network leading to fracture. (C) 2004 Elsevier B.V. All rights reserved.