Research On Microstructure And Properties Of Solid State Recycling And Formation Laws Of Rotary Extrusion For Mg-Gd-Y-Zn-Zr Alloy

Magnesium alloy,as a lightweight metal structure material,has a series of advantages such as low density,high specific strength,great damping and shock absorption,cutting,electromagnetic shielding performance,which is widely used in the fields of aerospace,automotive industry,electronic communications,etc.Adding rare earth elements such as Gd and Y,the microstructure and properties of magnesium alloys can be improved significantly.With the large-scale use of magnesium alloys products,their waste in the processing and production has also increased dramatically.Therefore,the solid state recycling of magnesium alloy waste can promote energy saving and emission reduction,which is conducive to the sustainable development of the magnesium alloy industry.Repetitive upsetting and extrusion and rotary extrusion are severe plastic deformation processes,which can refine grains and uniform structure,thereby improving the microstructure and properties of magnesium alloy materials.In this project,firstly,hot press sintering and spark plasma sintering were used to conduct solid state recycling experiments on as-cast Mg-7Gd-4Y-2Zn-0.4Zr alloy chips,and the microstructure and properties of the as-cast,hot press sintered and spark plasma sintered alloys were performed.Then through finite element simulation,the deformation laws of recycled rare earth magnesium alloy by rotary extrusion under different parameters were studied,and reasonable process parameters were determined.Finally,through finite element simulation,the repetitive upsetting and extrusion process to preform the blank was used to increase the accumulated deformation and improve the deformation uniformity of the rotary extruded forming parts,which provides technological reference for the research of solid state recycled rare earth magnesium alloy by repetitive upsetting and extrusion and rotary extrusion.The hot press sintering experiment under different temperature parameters and the spark plasma sintering experiment under optimal parameters were carried out on the rare earth magnesium alloy chips.Then microstructure analysis and properties test of as-cast and recycled rare earth magnesium alloys were tested.The results show that among hot press sintered recycled alloys,those obtained at the sintering temperature of 400℃ had better microstructure and properties,in which the dynamic recrystallization was completed and the grains were refined.The microstructure and properties of spark plasma sintered recycled alloys were the best in as-cast and recycled alloys,with a compressive strength of 479.4MPa and a ultimate compressive strain of 21.7%.Through finite element simulation of recycled rare earth magnesium alloy rotary extrusion process,the effects of rotary extrusion temperature,bottom die rotation speed and punch movement speed parameters on the temperature distribution,stress and strain distribution of the rotary extruded forming parts and the load and torque of dies were studied,and the dynamic recrystallization grain size analysis was conducted,which provides technological reference for the research of rotary extrusion process of solid state recycled rare earth magnesium alloy.The suitable parameters of rotary extrusion process in recycled rare earth magnesium alloy were determined,which are as follows: the rotary extrusion temperature is 400℃,the bottom die rotation speed is 1.57 rad/s,and the punch movement speed is 1.0 mm/s.Through finite element simulation of rotary extrusion process of recycled rare earth magnesium alloy by repetitive upsetting and extrusion preformed,the effects of repetitive upsetting and extrusion passes parameter on the temperature distribution,effective stress and strain distribution of repetitive upset and extruded performing blanks and rotary extruded forming parts and the load of die were studied,which provides technological reference for the research of rotary extrusion process of recycled rare earth magnesium alloy by repetitive upsetting and extrusion preformed.The results show that the effective stress of repetitive upset and extruded preforming blanks and rotary extruded forming parts increases with the number of repetitive upsetting and extrusion passes,and the difference between 4 passes and 3 passes is not much different.Therefore,the number of repetitive upsetting and extrusion passes is determined to be 3,which can not only achieve the ideal effect of increasing the accumulated deformation and improving the deformation uniformity of the rotary extruded forming parts,but also save manpower and material resources,and have high economic benefits.