Analysis of microstructure and properties of Mg/Al dissimilar joints by GTAW with Al-Si filler wire

Abstract

Mg/Al dissimilar materials were welded successfully by gas tungsten arc welding (GTAW) using SAlSi-1 and SAlSi-2 welding wire. The joints with good surface forming and free of defects were achieved. The Mg/Al welded joints were analyzed by means of optical microscope, scanning electron microscope and micro-sclerometer. The results show that the fusion area on magnesium side is obviously divided into columnar crystal zone and dendritic crystal zone. More intergranular precipitates were observed in dendritic crystal zone than in columnar crystal zone. However, the weld area is the typical columnar zone. No high microhardness brittle phase was observed in the fusion area near magnesium side. The microhardness of weld zone is slightly higher than magnesium base metal, and far lower than the Al base metal.K e y w o r d s : dissimilar material, GTAW, microstructure, microhardness