Microstructure and mechanical properties of as-cast Mg-9Gd-1.5Zn-xAl alloys
Mg-9Gd-1.5Zn-xAl(x=0,0.3,0.8 and 1.3 mass％)alloys were prepared by casting method.Effects of different Al contents on phase and microstructure of the Mg-9Gd-1.5Zn alloy were studied by X-ray diffraction,optical microscope and scanning electron microscopy,and the mechanical properties of the four alloys at room temperature were tested by an electronic tensile testing machine.The results show that the microstructure of the as-cast Mg-9Gd-1.5Zn alloy is composed of α-Mg matrix and Mg5Gd and(Mg,Zn)3Gd phases distributed along the grain boundaries.After the addition of Al element,the Mg5Gd phase in the alloy gradually decreases and new phases Al2Gd,Al11Gd3 and LPSO(Mg12Gd(Al,Zn))are formed in the alloy.The Al element promotes the formation of effective heterogeneous particles(Al2 Gd),inhibits grain growth,and significantly refines the microstructure of the alloy,achieving the effect of fine grain strengthening.When the addition amount of Al is 0.8％,the tensile strength,yield strength and elongation of the alloy are 192.2 MPa,154.8 MPa and 16.6％,respectively,compared with the Mg-9Gd-1.5Zn alloy without Al,which are increased by 47.1％,64.8％,and 121.3％,respectively.
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