Effect of Si and Mg Level on Microstructure and Properties of Al-Mg-Si-Li Alloys

The microstructure and properties of Al-Mg-Si-Li alloys were investigated.The microstructure was observed by optical microscopy,the phases were determined by X-rays,the mechamical properties were determined by tester,fracture morphology was observed by scanning electron microscopy.The result shows that the primary Si of alloy appears in the microstructure of the Al-Si-0.3Mg-1Li alloys with the increment of Si level.The more the Si content,the coarser and more irregular the primary Si becomes.Being modified by Al-P alloy,the primary Si is fine.Further,the tensile strength and the yield strength of the alloys are 255.0 MPa and 130.0 MPa with 15% Si.The tensile strength and the elongation of the Al-Si-Li alloys is improved with the addtion of magnesium.With the increment of Mg level,the α-Al and the primary Si phase are refined,the amount of primary Si decreases,the eutectic microstructure increases,so that the mechanical properties of the alloys increases.The mechanical properties of the alloys is poor as herringbone Mg2Si phase appears in the alloys by excessive Mg.