Study On Refinement Mechanisms Of Aluminum Alloy Solidification Treated By High Intensity Ultrasonic

With the development of manufacturing such as automobile, aviation and navigation industry, the needs of Al-Si alloys are increasing greatly because they have the characters of low density, low expansion coefficient, excellent wearing and corrosion resistance, and satisfied casting properties. But in the normal microstructures of casting Al-Si alloys, usually consist of coarse primary silicon and needle-like or lamellar eutectic silicon, which greatly aggravated the mechanical properties of these alloys. So the control the size of Si phase have became the most important and necessary processing for these alloys before using them. High intensity ultrasonic is a technology base on physics, mechanics, electronics, and materials etc. It is an applied technology that changes some aspects of objects or properties, or its speed is changed by ultrasonic energy. High intensity ultrasonic treatment is one of the effective ways to improve solidification structure and mechanical properties of metals in the process of metal solidification.Application of power ultrasound in Al-5%Si alloy solidification with different parameters, such as ultrasonic power, duration and ultrasonic depth, then observe metallographic structure of sample, find out the best parameters. The results indicate that high intensity ultrasonic treatment can help refine the grains with cavitation and acoustic stream. The cavitation can form powerful shock wave with high temperature and pressure, then accelerates the nucleation and restrains grains growth. With the stirring of acoustic streaming, the melt become uniformity.The probe of ultrasound apparatus has corrosion problem by the high temperature of alloys, Fe of stainless steel are fusing into melt have the effect on grain refinement, then compare two kinds of probe treatment the solidification of alloys. The results indicate that Fe play the heterogeneity nucleation role.