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.