Effects Of Minor Sc On Microstructure And Properties Of ZL205A

ZL205A alloy has high strength,good plasticity,toughness and corrosion resistance,widely used in aerospace and aircraft bearing structure.With the development of material science and aviation industry,higher requirements have been put forward for the performance of ZL205A alloy.Microalloying is an effective method to improve the properties of cast aluminum alloys.In this paper,the effects of Sc on the microstructure and properties of ZL205A in sand mold casting and water-cooled metal mold casting were studied by OM,SEM,TEM,hardness test,tensile performance test and fatigue performance test.,the conclusion is as follows:The experimental results show that the grain size of the alloy is refined with the increase of Sc content in the sand mold.When Sc content is greater than 0.1wt.%,AlCuSc phase is generated in the alloy,and the morphology of AlCuSc phase is divided into Stick and cluster.The eutectic microstructure with Sc content of0.22wt.%mainly consists of?-Al+Al₂Cu+W?AlCuSc?phase.Within the Sc element content?0-0.22wt.%?added in the experiment,the yield strength of the alloy in the as-cast state increased first and then decreased with the increase of Sc content.When the Sc content was 0.14wt.%,the yield strength of the alloy reached the maximum value of 118MPa.When Sc content is 0.03wt.%,the aging response rate and peak aging hardness of the alloy are close to that of ZL205A.When Sc exceeds 0.03wt.%,the aging response rate and peak aging hardness decrease with the increase of Sc,and the amount of precipitated phase decreases.When Sc content is within 0.1wt.%,the tensile strength of the alloy T6 state remains above 450MPa,and the Sc content exceeds 0.1wt.%.With the increase of Sc content,the tensile strength of the alloy decreases.When Sc content is 0.1wt.%,the fatigue performance of the alloy is the best.Compared with the sand mold casting,the water-cooled metal mold casting significantly refines the grain size,and the peak aging precipitate phase density and size in the alloy are larger.Water-cooled metal mold casting significantly improved the mechanical properties of the alloy.The tensile strength and elongation of the alloy containing 0.1wt.%Sc in sand mold casting were 447.8MPa and 2%,respectively.Using water-cooled metal mold casting method,the properties of the alloy were improved to 474.6MPa and 10.56%.