Local reinforcement of magnesium base castings with mild steel inserts

The functionality of structural light alloy castings can be considerably improved by inserting into them upon moulding iron base local reinforcements. A necessary condition to obtain tight joints with good load transfer is that a sound metallurgical bond is formed at the insert/alloy interface. However, many physical–chemical factors play an important part in the mechanical behaviour of the joint. To acquire a better insight into this issue, bimetallic samples were prepared by immersing a mild steel bar (5 mm in diameter) in magnesium base Mg–Al alloy melts held at 650–750 °C in a graphite crucible (mean diameter 19 mm). Different processing conditions were used to vary the degree of chemical interaction at the insert/alloy interface. After melt solidification, the bimetallic samples were cut into slices (2–10 mm thick) and push out testing was performed on these slices. Attempts have been made to relate the main features of the load–displacement curves thus obtained with the nature and extent of the transition zones formed at the insert/alloy interface.