Crystal Structure Analysis of Irradiated Ni₃Al Using Molecular Dynamics Simulation

Abstract

The structural changes of irradiated Ni₃Al were simulated by a molecular dynamics (MD) method. The irradiation event was modeled as the energy deposition of thermal energy produced by a high-energy ion beam, i.e. effective stopping power gSe. The L1₂ structure was taken as the initial structure and the effects of the irradiation event on the atomic structure were investigated. The relative degree of order, defined as the ratio of the calculated diffraction peaks of the L1₂ structure before and after the irradiation, and the number of site-exchanged atoms were calculated and found to show good correlation with gSe. The strength of the specimen was estimated from potential energy and it was decreased after the irradiation. Results of the uniaxial extension test done in the MD simulation suggest that the off-site atoms and site-exchanged atoms are the major cause of the reduction of specimen strength.

Fig. 5 Time changes of ordered L1₂ lattice structure in Ni₃Al after being irradiated with gSe = 2.0 keV/nm. Green spheres are atoms in the ordered L1₂ lattice structure and red spheres are recovered atoms from the disordered structure. Both green and red atoms are on fcc sites, while grey atoms are in the amorphous structure.