Radiation-induced amorphization of ordered intermetallic compounds CuTi, CuTi2, and Cu4Ti3: A molecular-dynamics study.

Abstract

Solid-state amorphization resulting from the introduction of chemical disorder and point defects in the ordered intermetallic compounds CuTi, ${\mathrm{CuTi}}_{2}$, and ${\mathrm{Cu}}_{4}$${\mathrm{Ti}}_{3}$ was investigated, with use of the isobaric-isothermal molecular-dynamics method in conjunction with embedded-atom potentials. Antisite defects were produced by randomly exchanging Cu and Ti atoms, and vacancies and interstitials were created by removing atoms at random from their normal sites and inserting atoms at random positions in the lattice, respectively. The potential energy, volume expansion, and pair-correlation function were calculated as functions of the numbers of atom exchanges and point defects. The results indicated that, although both chemical disordering and point-defect introduction increased the system energy and volume, the presence of point defects was essential to trigger the crystalline-to-amorphous transition. By comparing the pair-correlation function calculated after the introduction of point defects with that of the quenched liquid alloy, the critical damage dose (in dpa, displacements per atom) for amorphization was estimated for each compound: \ensuremath{\sim}0.7 dpa for CuTi, \ensuremath{\sim}0.5 dpa for ${\mathrm{CuTi}}_{2}$, and \ensuremath{\sim}0.6 dpa for ${\mathrm{Cu}}_{4}$${\mathrm{Ti}}_{3}$. At the onset of amorphization, the volume expansions were found to be \ensuremath{\sim}1.9%, \ensuremath{\sim}3.7%, and \ensuremath{\sim}1.7% for these respective compounds. In general, the results obtained in the present work are in good agreement with experimental observations.