Research On Semi-solid Continuous Forming Of Al-Mg-Sc Alloy

In this study,Al-Mg-Sc alloy wire was prepared by a semi-solid continuous forming method.The mechanical properties of Al-Mg-Sc alloy wire in this study are mainly dependent on the effective control of the semi-solid continuous forming process and the strengthening effect of Al₃Sc phase on the alloy.In this paper,we adopt the method of computational simulation+experimental verification to study the semi-solid continuous forming process of Al-Mg-Sc alloy from two aspects:microscopic and macroscopic.First,the process parameters were optimized for the semi-solid state continuous forming process.Solidworks software was used to build a 2D geometric model of the host section of the semi-solid continuous forming as a numerical simulation,and Deform-2D,a metal plastic forming software,was used to simulate the semi-solid continuous forming process to determine the changes of temperature,stress-strain,and velocity during the process.The controllable process parameters of pouring temperature,extrusion wheel speed,and running clearance were selected as reference factors for orthogonal tests to optimize the process parameters.Next,the first principle calculation software Materials Studio was used to calculate the structural parameters,elastic properties,heat of formation,and bonding energy of the Al₃Sc phase.Finally,experiments on the preparation of semi-solid continuously formed Al-Mg-Sc alloy wires were carried out based on the optimal process parameters provided by the numerical simulations,mechanical property measurement and microstructure observations were performed.The major research findings are as follows.The flow pattern of molten metal and the distribution characteristics of each physical field in the host of semi-solid continuous forming were obtained by numerical simulation method.The mold structure was optimized.On this basis,pouring temperature,extrusion wheel speed,and running clearance were selected as optimization factors,and load,deformation uniformity,and damage value were selected as optimization targets for orthogonal tests.The analysis indicated that the optimum process parameters were:pouring temperature 690°C,extrusion wheel speed 13 RPM,running gap 12 mm,etc.The lattice constants,elastic constants,heat of formation,and bonding energy of the Al₃Sc phase are calculated by first-principles calculation.The theory of the Al₃Sc phase as a non-homogeneous nucleation refiner was also verified from the perspective of first-principles calculations.The result of the mechanical property testing showed an improvement in the tensile strength and elongation of the alloy wire by 8 MPa and 1.6%,respectively,after the optimization of the process parameters.The hardness results showed that the wire of Al-Mg-Sc alloy had a hardness of 108.63 Hv.Microstructure experiments successfully observed the distribution characteristics and morphology of the phases in the Al-Mg-Sc alloy wire,including the primary Al₃Sc phase and the secondary Al₃Sc phase precipitated during the aging stage.The electron diffraction images of the selected area show the co-grid interface characteristics,which are also agreement with the results of first-principles calculations.The fracture analysis results indicate that the Al-Mg-Sc alloy wire is a ductile fracture,and the SEM image contains many tough nests,which is also agreement with the good tensile properties of the alloy wire.