On the formation and growth of intermetallic phases during interdiffusion between low-carbon steel and aluminum alloys

The formation of intermetallic reaction layers was investigated for interdiffusion between a low-carbon steel and commercially pure aluminum (99.99%) and between a low-carbon steel and an aluminum silicon alloy (Al-5 wt.% Si). Solid/solid, solid/semi-solid and solid/liquid diffusion couples were produced at both 600 and 675 degrees C. The total width of the reaction layer is governed mainly by the parabolic diffusion-controlled growth of the eta phase (Al5Fe2), which exhibits orientation-dependent growth kinetics. The addition of Si to Al, which is known to decelerate reaction layer growth in interdiffusion experiments with Al melts, was found to accelerate the reaction layer growth in solid/semi-solid interdiffusion experiments. This phenomenon is discussed in light of previous atomistic explanations and the apparent activation energy calculated for the growth of the eta phase (Al5Fe2). (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.