Influence Factors Of Aluminum Alloy Castings Porosity Formation

In this paper, the influence of some factors on aluminum alloy castings porosity formation was investigated, lnvestigated,hycluding content, solidification rate, crystallization temperature interval and pressure. The al-alloy castigs were perpared at different solidification rate by changing the casting method and wall thickness.The influence of soliditication rate on the gas porosity formation was analyzed.Two types of al-alloy with different crystallization temperature interval were prepared in the ersearch. And the influence of crystallization temperature interval on the gas porosity formation was analyzed. The argon gas purification method was used to refine the al-alloy liquid to prepare the castings at different hydrogen content. and the influence of hydrogen content on the gas porosity fortnation was nalyzed. In low pressure casting process, the: influence of pressure on the gas porosity formation was analyzed by changing the additional pressure on the molten al-alloy. The results showed that the rule of solute distribution in al-alloy solidification explained the formation of the gas porosity. At the low solidification rate, the width of the hydrogen supersaturation concentration area and the existing time increased in the front of solid liquid interphase, and the quantity and size of bas porosity would increased too. The solidification process of common al-alloys with narrow crystallization temperature interval of al-alloy was inclined to layered solidification. This process can reduce the tendency to dispersed shrinkage, increase the tendency of cavity shrinkage, and results in round aIld t1Ile gas porosities. While the solidification process of most al-alloys with wide crystallization temperature interval was inclined to volume solidification. The liquid was divided into a lot of small separated molten pools by thick equiax crystals, which led to the formation of irregular shrinkage cavitiesin the castings at last. The hydrogen content was the primary cause of gas porosity formation. The number of gas porosity of al-alloy castings was increased with increasing hydrogen content. After increasing the additional pressure on the Surface of molten al-alloy, the air bubble formation reduced, the gas porosity decreased, and the toierostructure of castings hecame tighter.