| The 7050 aluminum alloy has the advantages of low density,high strength,good fracture toughness and strong corrosion resistance.In recent years,it has been widely used in the manufacture of high iron sleeper beam,aircraft fuselage frame,wheel cabin wall and other important structural parts.Extrusion is one of the main forming methods of high-performance 7xxx aluminum alloy.The extrusion speed and extrusion temperature are the important technological conditions affecting the properties of the alloy.Therefore,the relationship between the temperature and strain of the extrusion process under different extrusion process conditions is studied.To improve the comprehensive performance of 7050 aluminum profiles,To provide theoretical basis for making the reasonable extrusion process of 7050 aluminum alloy.For this paper,the hot extrusion of 7050 aluminum alloy bars is the object.Using the method of simulation and experiment,First in the extrusion temperature is 420?,The influence of extrusion speed on the temperature field,strain field,average grain size distribution and microstructure and performance of extruded bar was studied when the extrusion speed was 15~75mm/min.The results show that: With the increase of extrusion speed,extrusion temperature rise and extrusion pressure gradually increase.When the extrusion speed is 75mm/min,the temperature rise is 26?;Maximum extrusion pressure is 1145.6N.The microstructure of extruded bar is composed of recrystallization,matrix and deformation.The compressive velocity is mainly in the range of 15~45mm/min,and is dominated by deformation tissue,while the extrusion speed is 60~75mm/min.The cross section of extruded bar is mainly composed of equiaxial grain.With the increase of extrusion speed,the average grain size decreases first and then increases.When the extrusion speed is 45mm/min,the minimum is 4?m,and the uniformity is the best.The extruded bar longitudinal section is arranged in a strip shape with deformation texture.As the extrusion speed increases,the distribution density of the deformation texture(Brass texture)increases first and then decreases.When the extrusion speed is 45mm/min,the maximum is achieved.As the squeezing extrusion speed increases,the hardness value of the alloy transverse and longitudinal section increases first and then decreases.When the extrusion speed was 45mm/min,the maximum was 95.6HV and 111.8HV.When the extrusion speed was 75mm/min,the hardness was the smallest,83.9HV and 94.2HV.Secondly,when the extrusion speed is 45mm/min,when the extrusion temperature is 350?~470? range,the influence of extrusion temperature on temperature field,strain field,average grain size distribution and organization and performance of bar material.The results show that: As the extrusion temperature increases,the equivalent strain of the die hole is gradually reduced,and the equivalent strain is reduced from 6.73 to 6.44.The maximum extrusion pressure gradually decreased,when the extrusion temperature was 470? and the minimum was 768.2N.The microstructure of bar is composed of recrystallization,matrix and deformation.As the extrusion temperature increases,the proportion of the matrix is basically the same,which is about 75%.The deformation tissue gradually decreased and the total recrystallization was gradually increased.The cross section of extruded bar is mainly composed of equiaxial grain.With the increase of extrusion temperature,the average grain size of the bar cross section gradually increased,and the maximum average grain size was 4.33?m.when the extrusion temperature was 470?.Extruded bar longitudinal section is arranged in a strip,the extruded bar longitudinal section is composed of deformation texture,shear texture and recrystallization texture.As the extrusion temperature increases,the hardness of bar transverse and longitudinal section is gradually reduced.When the extrusion temperature rises from 350? to 470?,the hardness of bar transverse and longitudinal section was reduced from 95.6HV and 99.4HV to 83.9HV and 89.4HV. |
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