Si元素对挤压铸造Al-5Mg-xSi合金微观组织的影响

Effects of Si Contents on Microstructure of Squeezing Cast Al-5Mg-xSi Alloys

使用Thermo-Calc软件模拟了不同Si含量的Al-5Mg-xSi合金组织,对具有不同组织特征的合金进行挤压铸造。结果表明,不含Si时,合金的组织为α-Al+少量β-Al_3Mg_2相;加入Si后,组织中开始出现α+Mg_2Si共晶,且随着Si含量增加,共晶组织含量逐渐增多,共晶形貌由细长条状转变为粗大的凹多边形块状。当Si含量为0.1%～1.4%时,合金的组织为α、α+Mg_2Si共晶、少量β相;当Si含量为1.5%～2.3%时,合金的组织为α、α+Mg_2Si共晶;Si含量继续增加时,合金组织中出现细长的Si晶粒。

Thermo-Calc was used to predict the microstructure of alloys with different Si contents,and the alloys with different microstructure characteristics were prepared by squeezing casting method.The results show that the microstructure of the alloy is composed ofα-Al matrix and a small amount ofβ-Al3Mg2 phase without Si.After the addition of Si,α-Al+Mg2Si eutectic phase appears.With the increase of Si contents,the contents of eutectic phase is gradually increased and its morphology is transferred from slender bars into massive concave polygon.With the Si contents of 0.1%~1.4%,the microstructure is composed of Al matrix,α+Mg2Si eutectic and a small amount of Al3Mg2 phase.With the Si contents of 1.5%~2.3%,the microstructure consists of Al matrix andα+Mg2Si eutectic.When the Si contents are further increased,the fibrous Si particles appear in the morphology.