近共晶Al-Si合金的晶粒细化

Grain refinement for near-hypoeutectic Al-Si alloys

研究了Al Sr变质剂和锆复合盐细化剂对高近共晶Al Si合金宏观/微观组织的影响。结果表明:单一Al Sr变质剂的加入,不仅改变了共晶硅的形貌,同时对合金的组织也有较明显的细化作用。这可能是由于锶的加入,改变了液态金属的结构,导致枝晶尖端前沿生长过冷度增加,降低了枝晶α(Al)固液界面能。当Al Sr变质剂和锆复合盐细化剂共同作用时,随着熔体中锆含量的增加,铸锭的晶粒度显著减小,当熔体的锆含量超过0.35%,可获得细小、分布均匀的等轴晶,其宏观晶粒尺寸为100～120μm。与Al Zr中间合金相比,无论是细化效果还是抗衰退的能力都优于中间合金。

The influence of Al-Sr modifier and Zr compound salt on marco/micro structure of near-hypoeutectic Al-Si alloys was investigated. Only the addition of Sr into Al-Si alloys could result in transition of eutectic silicon from coarse plate-like or acicular to fine fibrous, at the same time it had also a better refinement to the structure of alloys. The present of Sr in Al-Si alloys causes the changes of structures of liquid metals, and leads to the decreases of the solid-liquid interfacial energy of dendrite α(Al) and increases of the growth undercooling of dendrite tips. The combined addition of Al-Sr and Zr compound salt, with increaseing the Zr content, the grain size decreases obviously. Finer and evenly equiaxed dendrite α(Al) is attained with addition of 0.35% Zr, and the size of macrostructure grain is about 100120 μm. The Zr in compound salt forms into the Al-Si alloys melt, compared to Al-Zr master alloys, the ability of grain refinement and resistant fading are better than those of Al-Zr master alloys.