Effect of chemical composition on the microstructure, tensile properties and fatigue behavior of sand-cast Mg-Gd-Y-Zr alloy

Microstructures, tensile properties and high cycle fatigue behavior of sand-cast Mg-Gd-Y-Zr alloys with different Gd and Zr contents have been investigated. With decreasing Gd content from 9 to 11 wt%, the amount of eutectic phase in sand-cast Mg-xGd-3Y-0.5Zr alloys and of the β′ precipitates in peak-aged (T6) conditions decreased, and increasing Zr content from 0.3 to 0.5 wt% led to a decrease in the grain size. The variation of Gd content had a slight influence on the tensile properties, while Zr content had an obvious influence on the tensile properties particularly the elongation. Gd and Zr affected the fatigue behavior in different ways, i.e. the increase of Zr content improved the fatigue strength while the increase of Gd content extends the fatigue life under relatively high stress.