The structures and strengths of the joining interfaces between Mg-10mass%Al alloy and cast-in inserted transition metal cores have been investigated. Three kinds of core materials were examined: S20C carbon steel, SUS304 stainless steel and titanium. The Mg-Al alloy specimen had higher shear strength than the pure Mg specimen for every core material. Molten Mg does not react with these core materials. On the other hand, molten Mg-Al alloy reacts with each core material and produces metallurgical joint with the core. The Ti core provided highest shear strength
