The Effect Of Element Mg,Cu,Mn On Microstructure And Mechanical Properties Of Al-20Si Aluminium Alloy

Aluminium alloy has been used widely in automobile industry, space,aircraft,electronic, communication with its merits like low density,good heat conduction,good machinability and so on. The quantity of Aluminium used is only less than steel.In this paper, the effect of different elements on the hypereutectic Al-Si alloy was reseached. First of all, to determine the content of silicon in the hypereutectic Al-Si alloy. Three defferent contents of silicon in this research are 10%,20% and 30%. Determine the best content of silicon of the hypereutectic Al-Si alloy by comparing as-cast and heat treatmeant the microstructure and properties. From the result we can find as the increases of silicon content the tensile strength and elongation of the alloys both decreased,the hardness increased nomatter as-cast or heat treatment. After heat treatment the properties of the alloys are better than as-cast.After adding Mg element to the Al-20% Si alloy, the microstructure was improved because of reducing of eutectic silicon and primary silicon quantity. At the same time tensile strength and elongation of the alloys raising as the increasing of the silicon content. There is a peak of tensile strength and elongation of Al-20%Si-1.5Mg alloy, the tensile strength peak number is 162MPa and the elongation is 7.47%. After T6 heat treatment the properties of the alloy was improved while the eutectic silicon was became into short rod and globalization. The tensile strength peak number of Al-20%Si-1.5Mg is 334.33MPa.After adding Cu element to the Al-20%Si-1.5Mg alloy, the microstructure was defferent from the Al-20%Si-1.5Mg alloy. As the increasing of the Cu element content, the branch crystal was found in the microstructure. While the mechanical properties are raising firstly and then declining. The Al-20%Si-1.5Mg-0.1Cu alloy's tensile strength and elongation were maximum reach to 181.33MPa and 8.44%.After T6 heat treatment the grain size was smaller than as-cast. Tensile strength was raising while increasing the content of Cu element, and the elongation raised firstly then declined. The Al-20%Si-1.5Mg-0.3Cu alloy's elongation was more than other alloys reach to 7.99%.Mn element as a important added in the Al-20%Si-1.5Mg alloy to retard grain growth at the process of recrystallization and eliminate the effect of Fe element. After adding Mn element to the Al-20%Si-1.5Mg alloy, the microstructure was changed. The quantity of primary Si was rducing and the quantity needle-like second phase was increasing. The mechanical properties was raising firstly and then declining as the increasing content of Mn. There a peak of tensile strength and elongation when the Mn element content was 0.5%, the peak number were 198.33MPa and 8.09%.After T6 heat treatment the microstructure became thin and the mechanical properties became better. When the Mn element content was 0.5% the alloy's tensile strength reach to maximum 313.33MPa and the elongation was 10.12%.