Interface chemistry in aluminium alloy castings reinforced with iron base inserts

Bimetallic automotive components consisting of an Al-Si light alloy reinforced with a cast iron insert have been manufactured by gravity die moulding. Special precautions have been taken to ensure a uniform wetting of the insert by the liquid light alloy. Under these conditions, three intermetallic compounds are formed at the insert/alloy interface: eta (Al5Fe2), tau5 (Al7.4Fe2Si) and tau6 (Al4.5FeSi). Upon subsequent heat-treatment, tau2 (Al5Fe2Si2) and tau10 (Al12Fe5Si3) also appear. Growth of these compounds is discussed in terms of thermodynamics, kinetics and reaction mechanism in the Al-Fe and Al-Fe-Si systems. The effect of these chemical changes on the mechanical properties of the insert/alloy joint will be examined. (C) 2002 Elsevier Science Ltd. All rights reserved.