Microstructure Characteristics of TIG Welded Al-Mg Alloy with Small Amount Er Addition

Samples of Al-Mg-Mn-Zr-Er alloys were welded by the method of TIG welding. Microstructures of base metal and welded zones were analyzed by optical microscopy (OM), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). Particular emphasis was laid on the existence form of Er and its effect on the microstructure and the phase composition of the fusion zone. Results reveal that the trace rare earth element Er mainly exists in the form of primary and secondary Al3Er phase, which play significant roles of refining and strengthening the fusion zone. A characteristic Equiaxed Zone (EQZ) is obtained beside the fusion boundary between the partially melted zone and the fusion zone (FZ) due to the addition of Er.