Effect Of RE On Microstructure And Properties Of Al-Si-Cu Die Casting Aluminum Alloy

Al-Si-Cu aluminum alloy has many advantages, such as good fluidity, low density, good thermal stability, wear resistance and so on. It is widely used in the fields of automobile, ship,military industry and so on. Due to the poor toughness of casting aluminum alloy, In order to further improve the toughness of the alloy, the research object of this paper was ADC 12 die casting aluminum alloy, the alloying elements were Y, Ce and Nd with the content of 0-2 %respectively, the microstructure of ADC12 alloy was subjected to metamorphic refinement and the ADC 12 alloy was treated with heat treatment subsequently. Reduce the content of Cu and Fe, increase the content of Mn and Mg slightly, Preparation of AlxSi-0.55Cu-0.85Y-0.45Mn-0.45Mg-0.35Fe ?x=7.5, 8.5, 9.5, wt%? alloy. the phase composition and microstructure were analyzed by using ICP, XRD, OM and SEM, the tensile mechanical properties at room or high temperature, fluidity and impact toughness of the alloy were contrasted through using universal tensile testing machine, impact testing machine and spiral flow mold, therefore the best type,content and solution treatment parameters of alloying elements were determined, established the relationship between alloy composition, microstructure and properties, and provide a theoretical basis for the development of high toughness casting aluminum alloy. The main results as follows:?1? ADC12-xRE alloy is consisted of ?-Al, eutectic Si, Al₂Cu, Al₈SiFe2 and Al-RE phase.the rare earth elements of Y, Ce and Nd have an effect on the modification of ADC 12 alloy, the effect of modification are Y is the best, Ce is the second, Nd is the worst, when the content of Y is 0.85 %, the modification effect of ADC12 alloy reaches the best, and the microstructure of the as-cast alloy is obviously refined. Not only the primary ?-Al can be transformed from coarse dendrites into fine cell crystals and equiaxed crystals, and the needle eutectic silicon into small fibrous or granular with more uniform distribution, The number of equiaxed grains and granular eutectic silicon greatly increased, and the new Al3Y phase was obtained at the same time; the flow length, tensile strength, elongation and impact toughness are 1541 mm, 225 MPa,3.5 % and 10.8 J/cm2, respectively, while the as-cast ADC 12 alloy of that are 1287 mm , 188 MPa, 1.5 % and 3.8 J/cm2, respectively.?2? The microstructure of ADC 12 alloy is refined by means of solution treatment at 520?for 8 hours, the tensile strength, elongation and the impact toughness are about 205 MPa, 1.5 %and 7.4 J/cm2 respectively; the microstructure of ADC12-0.85Y eutectic silicon particles grow up, the tensile strength is 205 MPa, the elongation is improved, and the impact toughness of is improved greatly. It is shown that the toughness of solution treatment materials significantly improved compared with the as cast ADC 12-0.85Y alloy.?3? The microstructure of Al-8.5Si-0.55Cu-0.85Y-0.45Mn-0.45Mg-0.35Fe alloy is uniform, and part of the Al matrix changed from dendrite to equiaxed crystal, and the short rod eutectic Si increased. The alloy has excellent flow properties, but the tensile strength and elongation are 189 MPa and 2 %, respectively. The mechanical properties of the alloy are lower than that of the ADC 12-0.85Y alloy.