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采用Al-5Ti-B和Al-10Sr对AlSi7Mg合金进行细化和变质处理,研究不同的静置时间和重熔次数对AlSi7Mg合金组织和性能的影响。结果表明,在4 h的静置过程中,AlSi7Mg合金晶粒尺寸先减小后增加。熔体中Ti含量几乎保持不变,但是形核核心聚集沉淀,有效形核核心减少。Sr在静置4 h中产生烧损,所以共晶硅的变质效果严重衰退。重熔两次时,细化效果衰退不明显,Sr含量急剧减少,共晶硅的形貌恢复到变质前的状况。从静置和重熔的实验中发现,Sr含量低于0.004%时,对共晶硅的变质效果不显著。
Al-5Ti-B and Al-10Sr were used to refine and modify the AlSi7Mg alloy. The effects of different standing time and remelting times on the microstructure and properties of AlSi7Mg alloy were studied. The results show that the grain size of AlSi7Mg alloy first decreases and then increases during 4 h standing. The Ti content in the melt almost remains unchanged, but the nucleation of the nucleus aggregates and precipitates, and the nuclei of effective nucleation decrease. Sr was burned in standing for 4 h, so the metamorphism of silicon seriously deteriorated. Refining two times, the refinement effect of recession is not obvious, the sharp decline in Sr content, eutectic silicon morphology restored to pre-metamorphosis. From the experiments of standing and remelting, it is found that the effect of eutectic silicon is not significant when the content of Sr is less than 0.004%.