Influence Of Alloying And Filtration On The Microstructure And Properties Of Casting Al-Mg Alloy

The methods of obtaining high strength-toughness in present include alloying, purification and cleaning. From the tow aspects, the casting processing was established, mould was designed, and ten different alloys were prepared adopted metal mould cast based on a great deal of references. And filtration treatment was done to some alloys. The room-temperature mechanical properties of these alloys were tested. The microstructure and composition of these as-cast alloys were analyzed by using OM and SEM. The effect and law of minor Sc, Zr and filtration treatment on the mechanical properties and microstructures of alloys was investigated. The results were theoretical analyzed also. The results are as follows:When each element satisfies collocations demand as Sc0.4%-Zr0.1%-Si0.15%, the highest tensile strength was obtained by orthogonal experiment. The best scheme to elongation is Sc0.2%-Zr0.2%-Si0.15%.The research of alloying ZL303 with Sc and Zr showed that tensile strength and elongation was improved. Especially while the filled quantity of Sc was 0.4%, the tensile strength was obviously improved to 35%.Crosstie grain size and develop dendrites of ZL303 was observed though optical microscopy. Adding 0.2% Zr alone or 0.2% Sc and 0.1% Zr together to ZL303 can fine grains in some degree. For the alloy of adding 0.2% Sc, the dendritic structure is still coarse but the second-phase within the grains disappears. Adding 0.4%Sc to ZL303 obtains equiaxed structure. Primary Al3Sc and Al3(Sc,Zr)were observed though SEM and EDX.Tensile strength and elongation were improved with filtration treatment. Meanwhile, microstructures were fine in some degree.The strengthening include solution strengthening of Mg, grain fining strengthening of Sc and Zr , dispersoid strengthening of primary Al3Sc and Al(3Sc,Zr)and physics strengthening of filtration treatment.