Clarifying the mechanism of superheating effect and using it to enhance the ductility of cast Al-Si alloys via refining both Si and Al phase

近年来，基于电子束熔炼（EBM）过程中的过热效应，通过细化Si和Al的微观组织，获得了高达33%的AlSi 10 Mg合金室温拉伸塑性。因此，利用这种过热效应可以细化铸造Al-Si合金（包括Al-Si 10、Al-Si 20和Al-Si 30合金）的组织，从而提高其塑性和强度。较高的内熔池温度和快速的冷却速度使熔池内的熔体均匀。在冷却过程中，特别是当温度降至1300-1000 ℃时，Al和Si纳米团簇在凝固过程中形成细小的晶粒。在此基础上，对Al 10 Si、Al 20 Si和Al 30 Si表面进行了单珠强化试验。显微组织观察表明，EBM单珠对AlSi 10和AlSi 20合金的显微组织有明显的细化作用，但对AlSi 30合金只能重熔部分基体。

Recently, a high tensile ductility upto 33% at room temperature in AlSi10Mg alloy has been obtained via refining both the Si and Al microstructure based on the superheating effect during electron beam melting (EBM) manufacturing. Thus, the microstructure of cast Al-Si alloys (including Al-Si10, Al-Si20, and Al-Si30 alloys) is expected to be refined to enhance both the ductility and strength using this superheating effect.By now, the mechanism of superheating effect for refining the microstructure of Al-Si alloy using EBM building process has been investigated. The higher temperature inner melting pool and the fast-cooling rate make the homogeneous melt liquid inner melt pool. During the cooling process especially when the temperature is decreased to 1300-1000 ℃, the Al and Si nanocluster occurred and form the fine grains in the solidification. Beside that, the single bead experiment on the surface of Al10Si, Al20Si and Al30Si have been conducted. The microstructure observation showed that EBM single bead could refine the microstructure in AlSi10 and AlSi20 alloy, but only can remelt part of the Al matrix in AlSi30 alloy.