ATOMISTIC SIMULATIONS IN TERNARY NI-TI-AL ALLOYS

Two different interatomic potentials of the embedded atom type were de veloped for the Ni-Ti system by empirical fitting to the properties of B2 NiTi. For one of the potentials, the cohesive energy and unrelaxed APB energy of the B2 phase were adjusted to low temperature first pri nciple calculation values. For the other potential, the cohesive energ y was adjusted to the experimental values at high temperatures, where the B2 phase is stable. This second interatomic potential also succeed ed in predicting the stability of the D0(24) Ni3Ti phase with lattice parameters close to experimental values. The interatomic potentials us ed for the pure components are the same as those used in our previous work to derive Ni-Al potentials based on B2 NiAl and Ti-Al potentials based on TiAl. This allows the use of the present potentials in conjun ction with these previously derived interactions to study ternary Ni-T i-Al alloys. For both potentials developed here, the L2(1) phase in th e center of the pseudobinary NiAl-NiTi is predicted to be stable and t he lattice parameters given by the potentials are close to the experim ental values. The potentials predict that Ni substitutes for Al in T-r ich L1(2) Ti trialuminides and Ti substitutes for Al in Ni-rich NiAl. As a test for this ternary EAM model, we present calculations of the A PB energies in ternary cubic trialuminides and dislocation cores in Ni Al with Ti impurities.