Study On The Compound Modifier's Effect To The Microstructures And Properties Of The Al-13.5Si-3.0Cu-1.5Ni Alloy

Eeutectic Al-Si alloy with 12% silicon, as the piston material, is most widely used at home and abroad. This alloy can meet the general internal combustion engines characterized by excellent casting property, a low thermal expansion coefficient, low density and good wear resistance etc. However, with the development of the internal combustion engine, mechanical properties and high-temperature performance in particular are increasingly demanded. So, improving the high-temperature mechanical properties of piston materials become the focus of research in recent years.Adding strengthening elements into Al-Si alloy is commonly used method for improving the high temperature properties of Al-Si piston materials. For example, Cu,Ni and other strengthening elements are added into the Al-Si alloy. These elements can generate high-temperature strengthening phase in the alloy to improve high-temperature properties of piston alloys.Master alloy containing B, Ti and other alloy elements are commonly used as the effective grain refiner in Al-Si alloys. As matter of fact, the most widely used grain refiner is Al-5Ti-1B alloy. Besides, the P element can effectively change the shape of silicon phase and reduce its weakening effect on matrix structure. Especially adding the Al-Ti-B master alloy to Al-Si piston alloy modifiered by P element can further refine the eutectic cell and primary silicon. Mischmetal can also play a good metamorphism on the Al-Si alloy, especially for enhancing the high-temperature properties of alloys, and the rare-earth modifier has a long-term stability and remelting. Modifier alloys were prepared by melt-spun, made of amorphous, nanocrystalline or microcrystalline thin strips, then which were added to the matrix alloy to serve metamorphism more effectively, significantly improve the microstrctures and increase the mechanical properties of alloys.In this paper, the Cu-Ni master alloys were added into the ZL108 alloy, so a new type of Al-13.5Si-3.0Cu-1.5Ni melt was fabricated out, and then put the melt-spun Al-5Ti-1B, Cu-P master alloy and mischmetal as the compound modifier into the matrix melt to generate the metamorphosing effect. It was compared that the effects of metamorphism using unmetamorphic alloy with that metamorphosed using ordinary bulk alloy by observing both microstructure and testing both mechanical properties.Analysing results indicated that the microstructure and general mechanical properties of Al-13.5Si-3.0Cu-1.5Ni alloy metamorphosed by the trace of the rapid quenching treatment modifier were better, especially the high temperature properties of alloys modifiered by the rapid quenching mischmetal had been improved significantly. At last, strengthening mechanism of Al-13.5Si-3.0Cu-1.5Ni alloy metamorphosed by this new compound modifier was studied in this paper.