Diffusion and Plasticity of Submicrocrystalline Metals and Alloys

摘要

Comparative investigations of the diffusion in Submicrocrystalline and coarse-grained metals and alloys by means of direct measurements and indirect evaluations on the basis of experimentally obtained parameters of creep and superplastic flow were carried out. The diffusivity determination by secondary ion mass spectroscopy in pure metals (Ni, Ti, Cu) reveals the enhancement of a grain boundary diffusion coefficient in Submicrocrystalline materials produced by severe plastic deformation by factor of 1 to 5 comparison to that in coarse-grained materials. The diffusivity evaluation using parameters of diffusion controlled processes during creep of pure metals or superplastic flow of Al-based alloys also demonstrates an increase of the grain boundary diffusion coefficient by 1-2 orders of magnitude in Submicrocrystalline materials. The physical reasons for the enhanced grain boundary diffusivity in Submicrocrystalline state, relative to that in coarse-grained metals and alloys, are discussed.