DISLOCATION DYNAMICS AND MULTIPLICATION VIA ATOMISTIC SIMULATIONS

Molecular Dynamics simulations of edge dislocation mobility under stre ss in ordered L1(2) Ni3Al have been performed between 10K and 1000K, a nd at applied shear stresses ranging from 0.01 to 0.08 C-44 In this wa y it has been possible to determine the Peierls stress and mobility pa rameters as a function of stress and temperature. <001>{100} edge disl ocations were studied, which split into closely spaced partials under stress. Under all levels of applied stress (and at lower temperatures) the initial partial dislocations would intermittently stop moving and recombine, then dissociate and move again. In all cases the dislocati ons exhibited a soliton-like behavior: infinite acceleration at the on set of movement, and further movement at a steady velocity (which was only weakly dependent on stress) on the order of 25% of the acoustic s hear velocity. Nonclassical, highly non-linear behavior was observed i ndicating the probability that a soliton picture of dislocation motion is more appropriate than the classical, ''massive string'' model that is traditionally used. Furthermore, as both the temperature and the s tress were increased, dislocation multiplication became increasingly f requent, ultimately resulting in a spontaneous amorphisation transitio n which has signs of being a percolation process.