The development of Fe-Zn intermetallic compounds in solid Fe/Zn and Fe/Zn-Al diffusion couples during short-term annealing at 400 degrees C

The effect of aluminium alloying additions of up to 0.2wt.%Al to zinc in th e early-stage formation of Fe-Zn intermetallic compounds was studied by mea ns of diffusion couple experiments. Diffusion annealing was employed on Fe/ Zn, Fe/Zn-0.1wt.%Al and Fe/Zn-0.2wt.%Al couples at 400 degrees C for times ranging from 10 to 50 min. It was found that aluminium additions to the zin c alloy initially inhibited intermetallic compound formation. Furthermore, a localised phase was noted at the delta(p)/zeta interface in the ternary c ouples at short times (< 30 min) which also inhibited phase growth. However , this phase was noted to have dissolved on further annealing (greater than or equal to 40 min), with the intermetallic phases that formed growing mor e rapidly than the binary couple at these times. It was also noted that int ermetallic phase growth in the binary couple was dominated by the zeta phas e at short times, but delta(p) growth dominated at times greater than 30 mi n. In contrast, the relative rate of growth of the zeta and delta(p) phases in the ternary couples remained almost constant with annealing time. (C) 1 999 Elsevier Science S.A. All rights reserved.