Effect of Li on Al-Si Alloys Structure and Properties

Al-12Si alloys containing1%, 2% and 3% lithium were prepared. The alloys were melted by a vacuum induction furnace. The microstructure was observed by optical microscopy, tensile test was performed at a rate of 1mm•s-1. Hardness was determined by a Vicker’s hardness machine. Adding 1%Li to the of Al-12Si alloy, the alloy is modified and its structure is eutectic. When Li content is 2% or 3%, the structure is hyper-eutectic, and proeutectic Si-phases are present. The Al-12Si-1Li alloy has a tensile strength of 190MPa and an elongation of 1%. With the increment of lithium, the strength and elongation of Al-12Si containing Li alloys gradually decreases, because of the presence of proeutectic Si-phases. The alloys exhibits hardening behaviors when ageing at 200°C, and the hardness decreases to a value with the prolongation of the ageing time.