Effect of Fe content on fracture behavior of Ni–Mn–Fe–Ga ferromagnetic shape memory alloys

Abstract

The effect of Fe content on hardness and toughness of Ni48.7Mn30.1−xFexGa21.2 (x=0–11, number indicates at.%) alloys is investigated and the relationship between the fracture toughness and the fractography is discussed by observing the fracture morphology and analyzing the propagation of the crack. The micro-Vickers hardness results indicate that the hardness increases with increasing Fe content. The fracture toughness results indicate that Fe doping has improved the toughness of Ni–Mn–Ga alloys, and the toughness increases with increasing Fe content in Ni48.7Mn30.1−xFexGa21.2 (x=0–11) alloys. Fracture morphology shows typical intergranular fracture with rock candy pattern in the Ni48.7Mn30.1Ga21.2 (x=0) and river pattern cleavage fracture facets in the Ni48.7Mn19.1Fe11Ga21.2 (x=11) alloy. The fracture type changing from intergranular fracture to transgranular fracture is the main reason for the improved toughness of Ni–Mn–Ga alloys by addition of Fe.