Microstructure and properties of transient liquid phase bonding of AM60 Mg alloy to 304 stainless steel with Zn interlayer

To join AM60 to SS304 a 1 mu m layer of Zn was deposited on the Mg alloy side by sputtering. Through the TLP process, eutectic constituents of MgZn and Mg7Zn3 are solidified at the interface as the main intermetallics. Based on Mg concentration in different locations of the interface, either primary Mg or MgZn crystallize before the eutectic reaction. The interlayer connection to the AM60 side is stronger than that of SS304. The bond strength has a direct relationship to the area fraction of peeled interlayer from the AM60 side. At the SS304 interface, Zn reacts with steel to yield a thin sigma-FeZn phase where excess Ni was rejected into the liquid to form Mg2Ni precipitates. The strongest joint was processed at 470 degrees C for 30 min.