Effect of Al addition on microstructure, texture and mechanical properties of Mg-5Gd-2.5Y-2Zn alloy

In this paper, microstructure, texture and mechanical properties of as-rolled Mg-5Gd-2.5Y-2Zn-xAl (x = 0, 0.5, 1.0 and 1.5 wt%) alloys were investigated. It was found that the added Al changed the solidification and precipitation behaviour of the matrix alloy by the formation of the Al-RE (Al11(Y, Gd)3 and Al2(Y, Gd)) phases. Edge and surface cracks happened in the as-rolled Mg-5Gd-2.5Y-2Zn alloy disappeared after adding Al. Both the broken W phase and the two Al-RE particles can stimulate nucleation of dynamic recrystallization via particle stimulated nucleation (PSN) mechanism. The content, size and distribution of second phase particles were affinitive with the effect of PSN mechanism, and then affected the texture characteristics, such as intensity and orientation distribution. The elongation of the Mg-5Gd-2.5Y-2Zn alloy was pretty low, just about 4.4%. After the addition of Al, although there was a slight decrease in strength, the ductility was obviously increased. Especially, the elongation of the alloy with 1.0 wt% Al addition was about 16.4% which approached 4 times as high as the Mg-5Gd-2.5Y-2Zn alloy. Besides, Al addition significantly changed the fracture surface of the Mg-5Gd-2.5Y-2Zn alloy. In particular, as 1.0 wt% and 1.5 wt% Al was added, many deep dimples were clearly observed, which showed obvious ductile characteristics.