Reduction of shrinkage porosities in aluminum alloy castings by external pressure fl uctuation under gravity fi eld

Abstract

A novel method to improve the feeding capacity of ZL205A alloy castings by pressure fl uctuation during its solidifi cation process under gravity fi eld was proposed. The experiments were done in the graphite mould by applying the fl uctuation pressure at the top of the riser. Results of the X-ray inspection of castings and simulations of fl ow velocity of alloy melt and temperature fi eld show that the new method can effectively improve the feeding capacity and signifi cantly reduce the shrinkage in the castings. The mechanism of improving the feeding capacity by pressure fl uctuation is that the fl uctuating pressure can make the ZL205A alloy melt form a vibration wave in the melt. The vibration wave can intensify the convection of the melt, and therefore, break down the barrage from the feeding channel which forms during the solidifi cation process of the ZL205A alloy, improving the feeding capacity.

Keywords

• Fluctuation pressure
• shrinkage porosity
• ZL205A alloy
• gravity casting