Study On High-silicon Die Casting Aluminum Alloys With High Strength

This paper presents the properties and preparation method of a kind of die casting alloy with high strength. The related method of purifying,dehydrogenation and modification are provided. Testing result shows that the mechanical properties of alloy are perfect withσ_b=320 MPa,δ=1.7% and Brinell hardness=110HB. The number of primary silicon of unit area in the microstructure of die casting is very large ,and the size is very small, with the largest size of 18μm. Wear resistant property is sound. The gas tightness of die casting was done, and no leakage had been found for one minute under 1.5 MPa air pressur.The paper also explored the necessity of P modification on primary silicon of the alloy with high content of silicon. Result indicates that P modification and rapid solidification can make a reciprocal promotion effect. Effects of P modification on primary silicon of hypereutectic die casting aluminum alloys under different cooling rates are studied. It's found that the size variation of the primary silicon presents similar tendency with the raise of cooling rate, and there are explicit changing areas. P modification has perfect refining effect under different cooling rate. It is still active even under very high cooling rate. Primary silicon phases are refined perfectly, with double-action of rapid solidification and P modification.