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

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. (c) 2006 Elsevier B.V. All rights reserved.