Fracture behavior and structural transition of Ni46Mn33Ga17Cu4−Zr alloys

This study investigated the fracture behavior and structural transition of Ni 46 Mn 33 Ga 17 Cu 4− x Zr x ( x =0, 2, 4) alloys after undergoing quasi-static compression and ball milling. The introduction of Zr-rich second phase enhanced the compressive strength without improving the mechanical ductility of the alloys. The dispersed second phase formed weak interfacial bonding with the martensitic matrix, which resulted in the low plasticity. After ball milling, the dual phase alloy particles were separated to the second phase particles and the matrix phase particles. The average particle size was reduced with increasing Zr content since the size of the second phase particles was much smaller than that of the matrix particles. Moreover, the structure of the second phase was almost not changed by the ball milling. The martensitic transformation disappears for all the alloys after ball milling because of the disordering of the martensitic matrix. Post-annealing at 800 °C can restore the martensitic transformation of the Cu4 and Cu2Zr2 alloys but is not effective to restore that of the Zr4 alloy.