锑对铝硅合金变质效果的炉前快速热分析研究

Rapid Thermal Analysis on Modification Effects of Sb on Eutectic Si Phase in Al-Si Alloy

利用炉前快速热分析系统研究了锑(Sb)对Al Si7Mg合金中共晶硅的变质效果。借助热分析曲线和金相组织,研究了Sb的不同加入量及保温时间对合金的影响。与未变质时相比,加入0.1%~0.25%Sb后,合金的共晶生长温度TEG分别降低5.0~7.8℃,并出现明显的共晶再辉温升。保温时间由0.5 h增加至2.5 h,共晶硅相逐渐变短。当合金以较慢速度冷却时,Sb变质后的共晶硅在厚度方向上有一定程度的减小,而提高冷速会使变质效果显著提升,共晶组织呈现纤细的短棒状甚至近球形。Sb的加入会增加合金液相的过冷倾向,当变质剂含量增至0.2%后,少量Sb会以Mg_3Sb_2的形式在晶界析出。

The modification effects of antimony （Sb） on eutectic Si phase in AlSi7Mg alloy were investigated with the help of rapid thermal analysis system and metallographic microstructure. Different amount of the antimony and holding time were experimental variable. The addition of Sb ranging from 0.1% to 0.25% has decreased the growth temperature of the eutectic silicon （TEG） by 5.0 ℃ to 7.8 ℃ and preseilts obvious eutectic recalescence prior to eutectic growth. The morphology of eutectic Si appears the trend of being shortened with holding time extending from 0.5 h to 2.5 h. The size ofeutectic Si in width direction has been reduced to a certain extent when the alloy cooling down at slow rate. Whereas faster cooling rate could obtain superior modification effects, which could be changed from short rod to nearly granular particles. The supercooling tendency of melt has been increased with the addition of Sb. Small amount of high melting point compound Mg3Sb2 will be crystallized at grain boundary when the dose of modifier reaches or beyond 0.2% in AlSi7Mg alloy.