Effects Of Ti On Microstructures And Mechanics Properties Of Mg-containing High-silicon Aluminum Alloy

Al-Si alloy is of low density,high specific strength,heat resistance and wear resistance,good thermal stability and low thermal expansion coefficient,engine piston,cylinder head,cylinder,wheel yi and all kinds of mechanical and electrical products made of al-si alloy has a largrer service life than ordinary aluminum alloy components,which can be increased by 35%.Recently,because of the good qualities and wide prospect of application,high-silicon wrought aluminum alloy which is heat-treatable becomes research hotspot throughout the world.However,the research of the role that alloying elements play in high-silicon aluminum alloy ais still not rounded,especially the effect of Ti on the microstructure and mechanical properties of high-silicon aluminum alloy.Aimed at semi-continuous casting Al-12Si-0.7Mg-xTi aluminum alloy prepared by our laboratory,the purpose of the present study is to provide experimental data for enhancing the properties and structure of this alloy by studying the effect of the amount of Ti on the microstructure of alloy as cast condition,after single-stage homogenization,and twin-stage homogenization,based on which we further study on microstructure and mechanical properties of the Ti content in the hot rolled and cold rolled Al-12Si-0.7Mg alloy after solid solution-aging treatment,in order to optimize the best Ti content in Al-12Si-0.7Mg ingot and the best homogenization heat treatment process of Al-12Si-0.7Mg.The results of the study are as follows:1.Semi-continuous casting Al-12Si-0.7Mg alloy has coarse primary dendrite as well as wider primary dendritic arm spacing(PDAS).The primary dendrite and primary dendritic arm spacing(PDAS)of semi-continuous casting Al-12Si-0.7Mg alloy can be refined by Ti.The primary dendrite and primary dendritic arm spacing(PDAS)of semi-continuous casting Al-12Si-0.7Mg alloy is best refined when the amount of Ti content is 0.092%.when it is increased to 0.492%,the Refining effect weakened and there are large black blocks of TiA13 phase in the size of 20-50?m in the alloy matrix.2.After homogenization for semi-continuous casting Al-12Si-0.7Mg-xTi alloy,both of Al-Si eutectic phase and AlSiFe phase spheroidize,with the addition of Ti content,there is dispersed phase appears in the matrix.the amount of which is largest when the heattreatment process is 350?×8h+550?×24h,there are large black blocks of TiAl3 phase in the size of 20-50?m in the alloy matrix.3.Hot rolled and cold rolled Al-12Si-0.7Mg alloy being treated of solid solution aging treatment,bothAl-Si eutectic phase and AlFeSi spheroidize.with the addition of Ti,the grains arerefined,but Ti content increased from 0.092%to 0.492%does not make grain refinement better.4.Hot rolled and cold rolled Al-12Si-0.7Mg alloy being treated of solid solution aging treatment,yield strength and tensile strength and elongation rises first then falls with the increasement of Ti content.Both yield strength and tensile strength turn out to be higher when the alloy is treated in twin-stage homogenization.and both of them rise with the higher pretreatment temperature.5.The best Ti content in Al-12Si-0.7Mg is 0.092%,the best homogenization system of the alloy ingot is 350?×8h+550?×24h.after optimum homogenization treatment of hot rolled plate and manufacture again after solid solution aging treatment,the yield strength are 316.0 MPa and 286.8 MPa,respectively,tensile strength of which 342.5 MPa and 308.7 MPa,respectively elongation were 8.3%and 4.3%respectively.