Martensitic transformation and mechanical properties in an aged Ni-Mn-Ga-Ti ferromagnetic shape memory alloy

The martensitic transformation behavior and mechanical properties were investigated in a Ti-doped Ni53Mn23.5Ga18.5Ti5 alloy aged at 873 K for different durations. It is shown that the volume fraction of the Ni3Ti phase increases and the Ni content in the matrix reduces with increasing aging time, resulting in the decrease of the martensitic transformation temperatures. The precipitation of Ni3Ti particles strengthens the matrix, resulting in the increasing in the fracture toughness. Fracture morphology observation shows the fracture type changing from intergranular brittleness fracture to a mixture of intergranular and transgranular ductile failure is responsible for the improved mechanical proper-ties. (C) 2009 Elsevier B.V. All rights reserved.