The bonding of a mild steel insert to an AI-7Si alloy during squeeze casting has been studied for a range of processing conditions. Assessment of the mild steel/Al-7Si alloy interface shear strength has been made with a push-out test, and the results have been correlated with microstructural observations and residual stress calculations. Uncoated inserts do not exhibit any significant reaction with Al-7Si because of rapid cooling of the melt during squeeze casting, giving a low interface shear strength of similar to 30 MPa. Preheating the inserts to 900 degrees C slightly improves the interface shear strength to similar to 45 MPa, but reaction between the steel and Al-7Si is prevented by the formation of an Fe3O4 magnetite layer on the steel surface. Inserts hot-dipped in molten Al-10Fe before squeeze casting have a much greater interface shear strength of similar to 110 MPa, with failure in the Al-7Si matrix rather than at the steel/Al-7Si interface. Inserts vacuum plasma spray coated with titanium have the greatest interface shear strength of similar to 130 MPa, without any interface reaction, because of mechanical keying of the rough splat-quenched titanium surface combined with high residual stresses in the AI-7Si matrix.