Improved Defect Control and Mechanical Property Variation in High-Pressure Die Casting of A380 Alloy by High Shear Melt Conditioning

摘要

To promote mechanical properties and reduce the performance instability of A380 alloy produced by high-pressure die casting, a high shear melt conditioning (HSMC) technology was developed and applied to the melt prior to pouring into the shot sleeve. The experimental results show that, with the application of HSMC, the variation of elongation and yield strength was decreased from 21.8% and 5.5% to 13.9% and 3.6%, respectively. The improved mechanical performance is attributed to the enhanced heterogeneous nucleation in both the shot sleeve and the die-cavity of the die-caster, and also to the improved distribution of the secondary phases and reduced casting defects, including porosity, as a benefit of grain refinement induced by high shear. With the application of high shear, large numbers of the spinel phase (MgAl~(2)O~(4)) particles with double size distribution and average diameter of 80?nm and 300?nm were formed. Due to the good orientation relationship and small misfit between (α)-Al and MgAl~(2)O~(4), the particles act as effective nuclei in the shot sleeve and the die cavity, respectively.