Microstructure and Properties of Al-Si-Mg-Li Alloys

Microstructure and properties of the Al-7Si-0.5Mg-xLi (x=1, 2, 3) alloys were investigated. The microstructure was observed by optical microscopy, DSC was determined by a differential scanning calorimetry, and the hardness was determined by Vicker´s tester. The results show that the primary Si phases are present in the alloys. The amount and size of primary Si phase increase with the increment of Li content, and the shape of the primary Si phases become triangle from oval. Precipitates are inhibited by lithium to make the alloys being hardened poorly. The alloys have lower elongation and higher strength, and the elongation decreases with increment of Li level. The Al-7Si-0.5Mg-2Li alloy has the strength of 245MPa.