The diffusivity of 63Ni radiotracer in equal-channel angular processed Cu-0.17wt%Zr alloy was measured at 150 to 350C under conditions where no bulk diffusion occurred. Microstructural observations after annealing indicated that alloying with Zr was essential for stabilizing the equal-channel angular processed alloys against grain growth and recrystallization. In all of the samples studied, the experimentally measured diffusion profiles exhibited 2 distinct slopes. These were associated with so-called slow and fast short-circuit diffusion paths (table 4). The diffusivity along slow diffusion paths in the equal-channel angular processed samples coincided with diffusivity via relaxed grain boundaries in coarse-grained Cu; measured using the same radiotracer method at similar temperatures. The fast diffusion paths observed here were associated with the non-equilibrium grain boundaries produced by equal-channel angular processing.

Short-Circuit Diffusion in an Ultrafine-Grained Copper–Zirconium Alloy Produced by Equal Channel Angular Pressing. Y.Amouyal, S.V.Divinski, Y.Estrin, E.Rabkin: Acta Materialia, 2007, 55[17], 5968-79

Table 4

Diffusivity of 63Ni in Cu-0.17wt%Zr