Research On Preparation And Thixoforming Of Semi-solid Billet Of 5A06 Wrought Aluminum Alloy

There are many structural parts such as brackets,connecting rods,and angle frames in the fields of aerospace,weapons,ships,oceans and so on,which have both complex shapes and high mechanical performance requirements.It is difficult to meet the mechanical properties of the parts if the traditional casting is used,and if the traditional forging is used,it involves high production costs with low material utilization efficiency.So the best processing method of the parts is thixoforming,which can effectively implement the both requirements.In this paper,based on the thixoforming technology,with 5A06 wrought aluminum alloy as the raw materials,the microstructure evolution and its influencing factors during the semi-solid isothermal treatment were studied.And aimed at the shape characteristics and performance requirements of a typical aluminum alloy bracket in the aerospace field,the thixoforming was numerically simulated and the thixoforming experiment was conducted,finally,the microstructure and mechanical properties of parts produced by thixoforming technology have also been investigated.All the work in this paper will provide a certain theoretical and experimental basis for the further research and industrial application of the thixoforming technology in wrought aluminum alloys.The 5A06 aluminum alloy semi-solid billet was prepared by wrought aluminum alloy semi-solid isothermal treatment(WASSIT)directly.Then the influence of holding temperature and holding time on the microstructure was analyzed,and the microstructure evolution together with the growth mechanism of the grains was also discussed.The results show that,the suitable semi-solid billet preparation parameters range is the holding temperature at 610~615?,holding time at 15~20min,the optimal parameters is 615? with 20 min.As for the larger size raw materials,the semi-solid billet prepared by the WASSIT method has a slightly larger grain size and a lower roundness due to insufficient accumulation of deformation energy in the material before the isothermal treatment.The true stress-true strain curves of the material was obtained through semi-solid isothermal compression experiments.The curve data was imported into Deform-3D finite element software to establish the 5A06 aluminum alloy material model,and the thixoforming of the bracket was numerically simulated.The thixoforming process was analyzed and the influence of different parameters on the process was studied.Results show that the suitable process parameters for the thixoforming of the bracket are as follows: the billet temperature is 615?,the punch temperature is 350?,the die and the ejector pin temperature is 400?,and the loading speed is 10mm/s.The thixoforming experiment was conducted,the influence of process parameters on the properties of the part was discussed,the microstructure and mechanical properties of the formed parts at different locations were also analyzed.The results show that,thixoforming technology implements one-time integral forming of this typical aluminum alloy bracket and the formed parts have a good surface quality with a complete filling state,which improves greatly the material utilization efficiency.Significant plastic deformation occurs in the grains during the forming process,resulting in deformation strengthening effect,and it is benefit to the improvement of the mechanical performance.