交流电脉冲调控Al-7%Si合金中α-Al相形态演化机制

Morphology Evolution Mechanism ofα-Al Dendrite of Hypoeutectic Al-7%Si Alloy Regulated by Low Voltage Alternating Current Pulse

研究了低压交流电脉冲下Al-7%Si合金初生α-Al相的微观组织演化规律,数值模拟了合金熔体中的电流及电磁力分布,结合模型中嵌入金属网的方法,对电脉冲调控微观组织的机理进行了分析。结果表明,无论砂型还是金属网内、外,α-Al树枝晶随着脉冲电流密度的增大而更细化,然而部分组织形貌由树枝状向蔷薇状的转变与脉冲电流密度和位置都有关。相同的电脉冲下,当脉冲电流密度足够大时,砂型中与金属网内、外的α-Al相组织形貌存在显著差异。分析认为,初生α-Al相组织的变化主要是由脉冲电磁力驱动的熔体对流作用引起的;此外通过计算熔体流动状态雷诺数,预测了不同密度电脉冲作用下Al-7%Si合金中初生α-Al相的形貌。

The α-Al dendrite morphology evolution law of hypoeutectic Al-7% Si alloy under low voltage alternating current pulse （LACP） has been investigated in this paper. The distribution of current pulse and electromagnetic force in the alloy melt were numerically simulated. LACP of different current density was imposed in whole solidification process of the alloy and the wire metal tube was embedded in sand mould to restrain the melt convection. The mechanism of microstructure regulated by LACP was analyzed. The results show that the degree of refining of α-Al dendrite was aggravated with the increase of current pulse density in cas- ting samples of without wire metal tube and outside of wire metal tube and inside of wire metal tube. However, some of α-Al dendrites turn into rosiness from dendritic is related to the current density of LACP and location. There were significant differences in the morphology of the α-Al dendrite between casting samples of without wire metal tube and outside of wire metal tube and inside of wire metal tube. The analysis suggests that the change of α-Al dendrite was caused by melt convection resulted from the pulse electromagnetic force. The α-Al morphology can be predicted through calculating the Reynolds number of alloy melt, after Al-7% Si alloy was treated with different current density LACP.