Slow coarsening of B2-ordered domains at low temperatures: A kinetic MonteCarlo study

The kinetics of the ordering and coarsening of B2-ordered domains is studie d using atomistic kinetic Monte Carlo simulations. Special emphasis is put on the effect of annealing temperature, alloy composition, and tom dynamics on the coarsening behavior. When atomic diffusion proceeds by vacancy jump s to nearest-neighbor sites, a transient slow coarsening regime is observed at temperatures below half the order-disorder transition temperature T-c. It results in apparent coarsening exponents that decrease with decreasing t he annealing temperature. Values as low as 0.14 are measured at 0.25T(c). S low transients take place in both stoichiometric and nonstoichiometric allo ys. These regimes are correlated with the transient creation of excess anti sites during domain disappearance. Since antiphase boundary mobility decrea ses with increasing antisite concentration, this transient excess results i n the slow coarsening observed in simulations.