MATHEMATICAL-MODELING OF THE MECHANICAL ALLOYING KINETICS

A rigorous mathematical model, based on the modified iso-concentration contour migration method, has been developed to predict the kinetics of diffusive intermixing in a binary miscible system in the course of mechanical alloying (MA). The present model considers the variation of diffusion coefficient with composition, and interface shift due to bo th interdiffusion and mechanical deformation. Comparison of the kineti cs predicted by the present model with the relevant experimental data from Cu-Ni and Cu-Zn shows that the effective mass transport operative in MPI attains a rare intermediate between that for volume or grain b oundary diffusion. An effective temperature for diffusion (T-eff) has been proposed to simulate the observed alloying kinetics. T-eff is a f unction of composition but is not related to the adiabatic temperature rise at the point of ball-powder collision. Finally, the ratio of T-e ff to the corresponding liquidus temperature for all the composition s tudied lies between 0.4 and 0.5. (C) 1998 Acta Metallurgica Inc.