强磁场对亚共晶铝硅合金变质处理的影响

Effect of High Magnetic Filed on the Modification of Hypoeutectic Al-Si alloy

研究了强磁场对亚共晶铝硅合金变质处理的影响。对Al 6Si亚共晶铝硅合金进行Na盐变质处理后,重熔并在720℃下保温20min时,如果不施加强磁场,共晶Si呈粗大的针片状,长度和分布不均匀,凝固组织为未变质组织,即发生了重熔失效的现象。施加强磁场的条件下,共晶Si仍呈细小的颗粒状,凝固组织仍与第一次变质后相当,没有发生重熔失效的现象。分析认为重熔失效是Na的氧化和烧损以及凝固过程中对流的共同作用的结果。而施加强磁场的条件下,合金的变质组织得以保持是由于强磁场强烈抑制了熔体对流的。对固态下的合金施加强磁场对变质组织没有产生影响。

Effects of high magnetic filed on Al-6wt%Si hypoeutectic alloy modification was studied. It is found that the sample modified by Na-salt was kept 720℃ for 20 minutes under the condition without high magnetic filed,coarse plate-like or acicular eutectic Si appear on section of the sample and distribution of eutectic Si is unevenly;but under the condition with high magnetic filed,Eutectic Si become fine.It is thought that the reason why refusion of the sample did not make modification lose efficacy in high magnetic filed was the high magnetic field controlling convection of the melt.Effect of high magnetic filed on solidified structure is not observed at temperature below solidus.