Effect of high pressure rheological squeeze casting on hypereutectic Al Si alloy

Hypereutectic Al Si alloys have been widely used in the manufacture of automotive engine piston, cylinder block and other parts because of their high specific strength, good heat resistance and wear resistance. With the improvement of automobile engine power, the high-temperature strength and heat resistance of traditional cast aluminum alloy are approaching the limit state, which can not meet the development needs. Therefore, the research and development of high-strength and heat-resistant aluminum alloy materials has attracted much attention in recent years.

For the study of heat-resistant Al Si alloy, it is generally inclined to add elements with low equilibrium solid solubility and low diffusion rate in aluminum matrix, such as transition metal elements Fe, Ni, Cr, etc. the high temperature stable precipitates formed can improve the heat resistance of the alloy. Under the traditional casting process, the iron rich phase in the Fe containing aluminum alloy is coarse needle like, which seriously reduces the mechanical properties of the alloy at room temperature. Therefore, based on rapid solidification, researchers have developed horizontal flow casting, powder metallurgy and spray deposition technology. However, these methods are limited in industrial application due to their complex preparation process and limited product size. Ultrasonic treatment of Fe containing aluminum alloy melt is a new green and pollution-free technology, which has the advantages of simple process and low cost After ultrasonic treatment of Al Si alloy melt for a certain time, the iron rich phase in the alloy structure is still relatively coarse, and there is a certain amount of long needle like iron rich phase which cannot be eliminated. In addition to the alloy composition, melt treatment and cooling rate, pressure also has an important influence on the solidification structure. The conventional squeeze casting pressure (below 100MPa) can refine the iron rich phase in the aluminum alloy with low Fe content and reduce the adverse effect of iron on the room temperature properties of the alloy. However, a certain amount of long needle like iron rich phase still exists in the solidification structure of high Fe aluminum alloy under this condition. However, there are few reports on the high pressure solidification behavior of Al Si alloy.

Therefore, two groups of Al Si Alloys with different Fe content were designed. The effect of ultrasonic high pressure rheo squeeze casting on the iron rich phase and mechanical properties of the alloy was studied. The refining mechanism of the iron rich phase was mainly discussed.