Experimental study on diffusion induced recrystallization in Cu/Fe/Cu diffusion couples using Cu single crystals

Abstract

Diffusion induced recrystallization (DIR) in a face-centered-cubic (f.c.c.) Fe phase was experimentally studied in the Fe(Cu) system. The notation Fe(Cu) means that Cu atoms diffuse into a pure Fe or binary Fe-Cu phase. The Cu/Fe/Cu and Cu/(Fe-4.8Cu)/Cu diffusion couples consisting of a polycrystalline Fe phase specimen and pure Cu single crystals with the same crystallographic orientation were annealed at 1 193 and 1 323 K for various times between 3.0 × 102 and 8.6 × 104s. The penetration of Cu in the f.c.c. Fe phase was found to occur at rates 100 times greater than the one evaluated from the volume diffusion. This unusually rapid penetration is due to DIR, which takes place in the Fe phase from the interfaces of the diffusion couples. DIR was observed to occur only in the Cu/(Fe-4.8Cu)/Cu diffusion couples annealed at 1 323 K under the present experimental conditions. The thickness w of the Fe phase decreases with increasing annealing time t according to the equation W/W0 = 1 - 7.09 × 10-8(√t/W0), whereas the thickness l of the DIR region increases with increasing annealing time according to the equation l =1.58 × 10-6(t/t0)0.29. Here, W0 is the initial thickness of the Fe phase, and t0 is unit time, 1 s. The thicknesses W, W0 and l are measured in m, and the annealing time t is measured in s.