Formation of intermetallic compound in iron-aluminum alloys

The mechanism of iron and aluminum intermetallics formation in the reactive sintering of iron and aluminum mixing powders has been studied by investigating iron-aluminum diffusion couples. The couples were treated at 600°C, 700°C, 800°C, 900°C and 1000°C respectively. It was found that an Al-rich intermetallics FeAl₃ has formed in iron adjacent to the interface of iron and aluminum by aluminum diffusion into iron at 600°C (below the eutectic temperature), and that in the case above 700°C (above the eutectic temperature) there was a liquid, an intermetallics Fe₂Al₅ has formed in both side of the interface. The diffusion of iron and aluminum atoms is companied with the Fe-Al reaction during the treatment under the both conditions. The diffusion coefficients of iron and aluminum and the activation energy were determined. The mechanism of the intermetallics formation in the couples is also discussed.