EFFECTS OF 0.1 AND 0.2 WT.PERCENT ALUMINUM ADDITION TO ZINC ON THE INTERDIFFUSION BETWEEN ZINC AND IRON AT 400-DEGREES-C

This paper reports the interdiffusion behaviour between iron and zinc in Fe/Zn, Fe/Zn-0.1 wt.% Al, and Fe/Zn-0.2 wt.% Al couples annealed at 400 degrees C for times ranging from 1 to 30 h. Under steady-state gr owth conditions, the interdiffusion zone in the Fe/Zn and Fe/Zn-Al all oy couples consisted of intermetallic layers of the Fe-Zn phases T-Fe3 Zn10, delta(k)-FeZn7, delta(p)-FeZn10, and zeta-FeZn13. The intermetal lic layers grew at a more rapid rate in the Fe/Zn-Al alloy couples tha n in the Fe/Zn couple. The thickening kinetics of the total interdiffu sion zone in all couples were parabolic for annealing times greater th an 3 h. The compact delta structure (delta(k)) appeared at the Gamma/d elta(p), interface of the Fe/Zn couples after about 7 h annealing; whe reas, the same structure in either of the Fe/Zn-Al alloy couples was n ot observed until after about 13 h annealing. Enrichment of aluminium was detected at the delta(p)/zeta and zeta/eta-zinc interfaces in the Fe/Zn-Al couples. The extent of this enrichment was highest in the Fe/ Zn-0.2 wt.% Al couple. The aluminium enrichment is believed to have co ntributed to the increase in the thickening kinetics of the intermetal lic layers in the Fe/Zn-Al alloy couples owing to a negative thermodyn amic interaction between aluminium and zinc. (C) 1998 Elsevier Science S.A. All rights reserved.