Microstructure and mechanical properties of Gd-modified AZ80 magnesium alloys

The microstructure and mechanical properties of AZ80 alloy with different Gd contents were investigated. The results reveal that a minor addition of Gd could lead to a change in the type of second phase particles from Al–Mn to Al–Gd–Mn, and the primary rare earth phase is Al8GdMn4 instead of Al2Gd in the AZ80–0.3Gd alloy. New strip-like Al3Gd and block-shaped Al2Gd phases are formed successively with the increase of Gd content. Al2Gd phase becomes the dominating rare earth phase in AZ80–2.0Gd and AZ80–4.0Gd alloys. Tensile test indicates that the mechanical properties are improved obviously with a proper Gd content. However, excessive Gd addition results in the decrease of mechanical properties due to the formation of coarse block-shaped Al2Gd phase. AZ80–0.9Gd alloy exhibits the optimal mechanical properties among all the experimental alloys, in which the ultimate tensile strength (UTS), yield strength (YS) and elongation are 210, 130 MPa and 8.2%, respectively.