Previous results on phase evolution during mechanical attrition are reviewed. These are interpreted using the effective-temperature concept proposed by Martin (G. Martin, Phys. Rev. B30 (1984), p. 1424). The observed non-monotonic decomposition behavior is attributed to coupling between the evolving microstructure and phases. Previous experimental results and model of nanograin-size evolution in elemental Fe powder are employed to predict the dependence of the "ballistic" and thermal diffusion coefficients on the milling intensity and deformation behavior of the powder. These results lead to predictions on the dependence of the effective temperature, and therefore of alloy solubilities, on the hardness and milling intensity.