Effects of the pouring temperature on the formation of the bonding zone between AZ91 and AlSi17 in the compound casting process

The compound casting process was used to join AZ91 magnesium alloy to AlSi17 aluminium alloy. Liquid AZ91 was poured onto a solid AlSi17 insert placed in a steel mould heated to 370 °C. The experimental results showed that the temperature of the AZ91 melt affected the formation of the bonding zone between the two alloys. A continuous bonding zone was formed by applying a pouring temperature of 650 °C. The use of higher temperatures, i.e. 680 °C and 700 °C, did not lead to the formation of a continuous metallurgical transition zone at the AZ91/AlSi17 interface. The bonding zone was analysed using an optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray (EDS) detector. The structural constituents of the bonding zone near the AlSi17 alloy were: an Al₃Mg₂ intermetallic phase, primary Si particles surrounded by a rim of an Mg₂Si intermetallic phase and fine Mg₂Si particles. The area of the bonding zone that was adjacent to the AZ91 alloy had a eutectic structure composed of an Mg₁₇Al₁₂ intermetallic phase and a solid solution of Al and Si in Mg.