Based on the empirical electron theory of solids and molecules (EET), the phase valence electron structure parameters of Al-22%Si alloy are calculated, and the sensitivity of the bond network of Al-Si alloy melt to temperature (energy) and the effect of the sensitivity on the morphology are studied. The results show that the Si-Si clusters with larger nA in the slightly superheated Al-Si alloy melt supply the nucleation core to the primary silicon phase in the hypereutectic Al-22%Si alloy, and strongly generate the drag-like effect for the Al-Si clusters around them; that the variation of temperature significantly affects the stability of bonds of the core so that the solidified structure is changed; that the electric pulse applied to the alloy melt can irrecoverably alter the stability of Si-Si clusters, then the modifica- tion of the solidified structure morphology of alloys is generated; that the higher the energy of the electric pulse, the less stable the Si-Si clusters, and the more significant the electric pulse modification.
The metallographic structure of LM-29 aluminum-silicon alloy modified by electric pulse treatment has been investigated and compared with those untreated.The solidification structure of LM-29 alloy has been analyzed by means of M1AP3 Quantimet image processing and analysis system,and then the solidification process has been analyzed by means of differential scanning calorimetry(DSC).The results indicate that the primary silicon phase was refined remarkably by electric pulse while the tensile strength and elongation properties increased accordingly.Electric pulse treatment can also increase the binding power between silicon clusters and alloy melt matrix,as a result,the precipitation of primary silicon phase is suppressed to meet the demand of supercooling degree for nucleating,correspondingly.The electric pulse modification has great influence on the size of silicon atomic cluster as well as its distribution in the melt,subsequently,leads to the refinement of solidification structure.
He LijiaWang JianzhongQi JingangDu HuilingZhao Zuofu
