Preparation Of Al-Si Alloy Modifier And Study On Modification Effect

Hypereutectic Al-Si alloy is the most ideal alloy for piston materials in automotive internal combustion engine because of its excellent comprehensive performance. However, coarse plate-like primary silicon is present in the hypereutectic Al-Si alloy without modification, which can separate the matrix seriously and worsen comprehensive performance of the Al-Si alloy. Therefore, hypereutectic Al-Si alloy should have a refined processing before using it. Now it is generally believed that refining aluminum silicon alloy with phosphorus modification agent is the most cost-effective method.The paper puts forward a method which combines powder metallurgy with equal channel angular pressing to produce Al-P master alloy directly in order to overcome the shortcomings of Al-P master alloy reported, such as high modification temperature of Al-P master alloy(830℃), long modification time(more than 30min) and complex preparation technology. Equal channel angular extrusion can make the mixed powder deformed and a new and dense interface present after extrusion deformation, which can provide a favorable condition for the reaction of aluminum phosphate, then obtaining Al-P master alloy through powder sintering process. The experiment showed that the uniform mixture of aluminum and phosphate powder were extruded by the equal channel angular extrusion, the modificator were sintered for 40 min at 570℃ and A390 alloy solution metamorphic were added at 780℃. And then, it dissolve rapidly with a short time and the average size of primary silicon was deceased to 22μm, which precedes the known modificator. The online modification can be realized because of a decreased modification temperature and a short time of incubation, which make the aluminum alloy melt without overheating, save energy and improve the quality of the alloy melting.The method has the advantages of simple process, low cost and pollution-free modifycation process and preparation.