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Study Of Aluminum Alloy With High Volume Fraction Of Silicon Fabricated By Adding Silicon Particles In Aluminum Melt Using Mechanical Stirring Process

Posted on:2011-08-10Degree:MasterType:Thesis
Country:ChinaCandidate:Z L XiaoFull Text:PDF
GTID:2121360308473397Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
The high Si-containing Al-Si alloys are widely used in the automobile and motorcycle engine piston, because they have wear resistance, low linear expansion coefficient, good corrosion resistance and excellent casting capability. They are especially used for the manufacture of lightweight, wear-resistant high-temperature parts. In this paper, the high Si-containing Al-Si alloys were prepared by adding silicon particles into Al alloy through stirring process. The influence of stirring casting process parameters on the microstructure and properties of high-silicon aluminum alloys was investigated. Based on preparation out of Al-20% Si, the isothermal treatment on the alloy for improving its microstructures was studied. Then, the wear resistance of the high Si-containing Al-Si alloys were investigated.Firstly, the high Si-containing Al-Si alloy were prepared by adding silicon particles into Al alloy through mechanical stirring process. The high-temperature preheating Si particles were directly putted into the molten metal by high speed mechanical stirring, which made Si particles distribute throughout the metal melt, then let the Al alloy solidified in the air. In the preparation process of high-silicon Al-Si alloy, the effects of the factor such as surface pre-treatment process of Si particles on, the initial temperature of stirring, stirring speed and stirring time on the microstructure of the alloy, and the Si particle morphology before and after adding into the liquid were also studied. The experimental results showed that the mechanical stirring process can prepare the high Si-containing Al-Si alloys with Si volume fraction up 20%to 25%, and the roundness as well as distribution of the Si phase in the alloys are good. The mechanical stirring process temperature for preparing high Si-containing Al-Si alloys should be controlled between 700℃~720℃, and the stirring time should be 3-4 minutes. The roundness as well as distribution of the Si phases in the alloys by proper preservation of the high Si-containing Al-Si alloys.Secondly, the high Si-containing Al-Si alloy were prepared by adding silicon particles into Al alloy through mechanical mixing, because the wetting property between Si particles and liquid aluminum are bad, Si particles can not be completely dispersed in to liquid,it may lead internal defects in the alloy. Therefore, the high silicon aluminum alloy which prepared by mechanical mixing were isothermal heat treated in semi-solid states, to improve the microstructure and the properties of the alloys. The experimental results showed that semi-solid isothermal treatment can further improve the distribution of silicon particles in the alloy. It can be concluded that the proper insulation temperature is 580℃~600℃, but with increase in temperature, primary silicon become coarser. The hardness of the aluminum alloy after isothermal treatment at different temperatures correspond to the change in the alloy microstructure.The hardness of the alloys increased with increasing the isothermal temperature at first and then decreased.Lastly, the wear resistance of Al-Si alloys which are prepared by mechanical mixing were studied. The experimental results showed that high-silicon aluminum alloy prepared by mechanical stirring added Si particles to improve wear resistance. The wear resistance of materials was increased with the increasing content of Si particles, but the content is too high, the wear resistance decreased again. Because the high content of Si particles, with bad wetting property, at high-speed stirring caused the alloy shedding a large number of particles in the wear processes, thus affecting the wear resistance of materials.
Keywords/Search Tags:Al-Si alloy of high Si-content, Silicon particles, Mechanical stirring, Isothermal treatment, Microstructure, wear resistance
PDF Full Text Request
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