Dispersion of Shrinkage Cavity in Aluminum Alloy Castings Using Ultrasonic Melt Treatment for Generating Microbubbles

摘要

The size of defects in castings affects mechanical properties such as fatigue strength. These properties are the most important properties used for designing aluminum alloy casting components, and usually increase with decreasing size of internal defects. Large internal defects mainly form due to the volumetric shrinkage of melt at the last solidified position. In this study, we therefore examined the possibility of generating microbubbles in aluminum alloy melts for dispersing internal defects in castings.Ultrasonic treatment was used for generating nitrogen or argon microbubbles in the melt and was found to be suitable for forming fine gas porosities dispersed in castings. The fine gas remained in the melt for 3600 s, and the generated argon gas was detected from the porosities in the castings. The ultrasonic treatment could also remove inclusions and hydrogen in the melt. Moreover, the fine gas porosities in castings did not decreases the tensile strength of the castings.