高含铁量铝硅合金中铁相的凝固行为与形貌控制

Solidification Behaviors and Microstructure Morphology of Iron Phase in Al-Si Alloys with Higher Iron Content

研究了较高含铁量的铝硅合金中 ,铁相在不同合金成分、冷却速度以及不同含锰量下的凝固行为和微观组织形貌 .对α铁相基于β铁相形核长大的现象进行了分析 ,并对铁相的形核理论进行了初步的探讨 .结果表明 ,在含铁 1 .4% (质量分数 )的铝硅合金中 ,加 0 .7%的锰能使铁以α相的形式凝固 ,但冷速较高时 ,不能完全避免针状铁相的出现 ;锰的加入量增加到 1 .4% (Fe/Mn=1∶1 )时 ,较高冷速下 ,仍有针状铁相出现 ,且使初生铁相更加粗大 .在同样的铁锰含量下 ,亚共晶铝硅合金中的初生铁相明显比共晶合金要少 ,且 α铁相在 α铝树枝晶中会形成一种细密的树枝晶结构 ,可以作为基体的强化相 .

The solidification behaviors and microstructure morphology of the iron phases of Al Si alloys with higher iron content and different alloy compositions, cooling rates and manganese contents were studied. The phenomena of nucleation and growth of α phase based on β phase were analyzed and discussed. The mechanism of nucleation of iron phases was investigated primarily. Addition of 0.7%Mn to 1.4%Fe alloys can make iron phase form in α phase, but can not totally avoid needle like iron phase with the higher cooling rates, even 1.4%Mn addition (Fe/Mn=1∶1). With the same Fe and Mn content, the primary iron phase in the hypoeutectic alloys is obviously less than that in the eutectic alloys, and α iron phase will form a kind of thin dendrite structure in α Al dendrite crystal and will have strengthen effect. It is considered that the different crystal structures of solidified iron phases are not dependent on the nucleation.