Metal Mold Design Of Tensile Specimen An RE Strengthening Of Aluminum Alloy

A357 alloys are becoming one of the popular cast aluminum alloys used in the aerospace and automobile industry because of its castabililty,high corrosion high strength to weight ratio and coefficient of thermal expansion.When the mechanical properties of the A357 alloy are investigated,the experimental data are obtained using tensile specimens to save time and cost.The mechanical properties of A357 alloy are affected with porosity and microstructure.Therefore,it is significance to study the permanent mold of tensile sample so that can reflect the mechanical properties of the material,optimize the process parameters,and strengthen the properties of tensile sample.A357 is used as the raw material.Firstly,the prediction model is established by the RSM and the NSGA-II algorithm is used for multi-objective optimization to determine the process parameters of the permanent casting.Then the permanent mold is optimized,and then the Ce is added to strengthen the A357 alloy.XRF,OM,SEM,EDS,XRD and electronic universal testing machine are used to study the microstructure and mechanical properties effects of the optimized permanent mold and the addition of Ce strengthen.The results show that the optimal process parameters are pouring temperature 695 ?,mold temperature 290 ? and time 8-9 s.The casting defects and mechanical properties of the tensile specimen are improved.The SDAS is 33.2 ?m,the tensile strength is 215 MPa,the yield strength is 173 MPa,and the elongation is 4.5% of the sample.The addition of rare can cause the primary ?-Al phase to be refined and the morphology of the eutectic Si is improved,and the mechanical properties are improved.When the amount of Ce was 0.16%,the primary ?-Al phase and SDAS decreased to 39.54 ?m,21.16 ?m and 28.29 ?m,17.32 ?m under as-cast and T6 heat treatment.The length of eutectic Si is shortened 52.49% and 43.12%,and the aspect ratio is reduced 72.06% and 76.35%.The tensile strength increased 22.34% and 18.36%,the yield strength increased about 11.79% and 21.55%,and the elongation increased 41.15% and 58.82%.The optimized permanent mold of tensile sample can reflect the mechanical properties of the material more accurately.The optimized pouring process parameters and the amount of Ce have important practical guiding significance for obtaining high quality castings and improving the mechanical properties of A357 casting alloy.Figure 52;Table 16;Reference 76...