Energetic ion beam induced crystal phase transformation and resulting hardness change in Ni3Al intermetallic compound

The Ni3Al bulk intermetallic compound was irradiated with 5.4-MeV Al, 10-MeV I and 16-MeV Au ions at room temperature. The effect of irradiation on the lattice structure was observed by X-ray diffraction (XRD). The change in Vickers hardness by irradiation was estimated. A crystal structure analysis showed that, the Ni3Al lattice structure transforms from an ordered L12 lattice structure to a disordered A1 (fcc) lattice structure by energetic ion irradiation. The relative degree of order correlates well with the density of energy that was elastically deposited by irradiation. The Vickers hardness tends to decrease with an increase in ion fluence. The hardness is not correlated with the elastically deposited energy. The effect of annealing at elevated temperatures on the irradiation induced crystal phase transformation and the Vickers hardness is also discussed.