利用扫描电子显微术、X射线衍射、电化学测量技术以及浸泡腐蚀实验,研究添加钪的Al?6.5Si?0.45Mg铸造合金的显微组织和腐蚀行为,并且与锶变质合金的实验结果进行比较.结果表明:钪对合金的初生 α(Al)相和共晶硅相有明显的细化和变质效果,随着钪含量的增加,效果增强.当钪含量增加到0.58％(质量分数)时,钪对共晶硅相的变质效果几乎与锶的变质效果相当.与锶相比,钪可以改善实验合金在NaCl水溶液中的耐腐蚀性能,但过高的钪含量并不能进一步增强合金的耐蚀性.合金的腐蚀主要发生在合金的共晶区,且主要是共晶α(Al)被溶解,这证实了共晶硅相比α(Al)相具有更高惰性,并可在共晶硅与α(Al)相之间形成腐蚀电池.“,”The microstructures and corrosion behaviors of the Al?6.5Si?0.45Mg casting alloys with the addition of Sc were investigated by using scanning electron microscopy, X-ray diffraction, electrochemical measurement techniques and immersion corrosion tests and compared with those of Sr-modified alloy. The results show that Sc has evident refining and modifying effects on the primary α(Al) and the eutectic Si phase of the alloy, and the effects can be enhanced with the increase of Sc content. When the Sc content is increased to 0.58 wt.％, its modifying effect on the eutectic Si is almost same as that of Sr. Sc can improve the corrosion resistance of the test alloy in NaCl solution when compared with Sr, but the excessively high Sc content cannot further increase the corrosion resistance of the alloy. The corrosion of the alloys mainly occurs in the eutectic region of the alloy, and mostly the eutectic α(Al) is dissolved. This confirms that Si phase is more noble than α(Al) phase, and the galvanic couplings can be formed between the eutectic Si and α(Al) phases.