Recrystallization Behavior And Texture Evolution Of AZ31 Magnesium Alloy By Interactive Alternating Extrusion

With the goal of carbon neutralization,the concept of lightweight has been deeply rooted in people’s minds.Magnesium alloys can reduce weight and have superior mechanical properties,cutting properties,and damping properties at the same time.As a result,magnesium alloys can shine brightly in aerospace,rail transit,weapons and equipment,and other fields.However,magnesium alloys with dense hexagonal structures have poor plasticity due to their small number of slip systems.At present,a fine-grained strengthening strategy is widely used to obtain magnesium alloys with better strength and plasticity.Compared with other processes,the extrusion process can maximize the deformation of the blank,the surface quality of the extruded products is very high,and the overall performance is also good.However,there are some problems such as high energy consumption,uneven product organization,and low yield.The alternating extrusion technology ingeniously designs the punch as a split structure,which is mainly because the split structure can reduce the actual extrusion ratio in the forming process,thereby reducing the extrusion load.In addition,the alternating extrusion technology reduces the dead zone of metal flow in traditional extrusion and improves the utilization rate of materials.In this paper,AZ31 is used as a carrier to study the recrystallization mechanism and texture evolution of magnesium alloy under alternative extrusion.The relationship between the grain size and the strength and toughness of magnesium alloy was studied by means of metallography and tensile test at room temperature.The microstructure evolution and grain refinement behavior of magnesium alloy during extrusion were analyzed in detail by means of scanning electron microscope and elec tron backscatter diffraction(EBSD).In this paper,the microstructures under different extrusion ratios in the interactive alternative extrusion process were studied.When the extrusion ratio is 15.68,the grain refinement is obvious.When the extrusion ratio increases,the temperature rise caused by friction heat and deformation heat has a significant effect on the grain size.At higher temperatures,the diffusion rate of solute atoms and the corresponding driving force of gr ain boundary migration will increase,reducing the drag effect of solute,thus making the grain size relatively large.In the process of extrusion with different reduction,the average grain size is inversely proportional to the reduction.Under the combined effect of continuous dynam ic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX),the grains are refined to varying degrees,especially the magnesium alloy with the maximum reduction has the highest refining degree.Based on the above,the influence of pre-deformation on the mutual alternative extrusion of magnesium alloy is also explored.The predeformation can reduce the texture strength of the original billet,refine the grain,and optimize the secondary processing performance.After predeformation,part of the grain base plane inclines to the ED direction,forming a typical shear texture like that in equal channel angular extrusion.On this basis,the plasticity of magnesium alloy has broken through the shackles of traditional processing methods and rea ched the ideal value.