Effect Of Extrusion Technology On Microstructure And Properties Of Al-Zn-Mg Alloy

Al-Zn-Mg alloy belongs to medium and high strength aluminium alloy.Because of its high specific strength,light weight and good processing performance,it is widely used in aerospace,rail transit,building bridges and all aspects of civil life.Extrusion processing technology plays an important role in the processing of non-ferrous metals.It has the advantages of simple operation,high productivity and material saving.Dynamic recovery and dynamic recrystallization occur in the process of extrusion processing of aluminium alloy.Recrystallization degree will have an important impact on the comprehensive properties of the sample.This subject studied different extrusion methods.The relationship between microstructures and properties of AA7003 aluminium alloy with and without recrystallization inhibitors was studied.The effects of different extrusion processes on texture types and texture strength were also studied.Firstly,the effect of different content of Cu on the structure and properties of Al-Zn-Mg alloy was studied.It was found that the microstructure of as-cast Al-Zn-Mg-Cu alloy rod was mainly composed ofα-Al dendrite and intergranular eutectic phase by observing the microstructure of as-cast Al-Zn-Mg-Cu alloy rod.With the addition of Cu,the volume fraction of intergranular eutectic phase decreases,the grain boundary becomes narrow and discontinuous.XRD tests show that the second phases in the extruded sheet are mainly MgZn₂phase,Al₂CuMg phase and AlZnMgCu quaternary non-equilibrium eutectic phase.With the increase of Cu content,the tensile strength and yield strength of the alloy increase,but the elongation increases first and then decreases.When the content of u is 0.4%,the elongation of the alloy is the highest,which is 10.9%.When the content of Cu is 0.6%,the tensile strength is 430MPa.The relationship between the microstructures and properties of extruded AA7003aluminum alloy was studied under different extrusion processes.The results show that when the extrusion temperature is 430℃and the extrusion speed is 1mm/s,the grains of AA7003aluminium alloy with restraining recrystallization elements are elongated along the extrusion direction,showing fibrous shape.There are recrystallized grains directly between the adjacent fiber grains,and the grain boundary is serrated.With the increase of extrusion temperature,cubic texture appears in the structure and the strength of cubic texture increases.The strength of S texture decreases,and the recrystallization degree is the greatest when extrusion temperature is 450℃and extrusion speed is 1 mm/s.At this time,the strength of brass texture is the greatest,which is 9.060.The maximum elongation of the alloy is 13.9%when the extrusion temperature is 470℃and the extrusion speed is 1 mm/s.When extrusion temperature is 430℃and extrusion speed is 1mm/s,S texture,Goss texture and brass texture exist under different extrusion processes.The grain size of AA7003 aluminum alloy without restraining recrystallization element is equiaxed.The maximum elongation is 20.88%at extrusion temperature 470℃and extrusion speed of 1mm/s.At this time,the strength of cubic texture is the highest and the recrystallization degree of the alloy is the highest.The S texture strength increases with the increase of extrusion speed when extrusion temperature is 510℃.When extrusion speed is 4 mm/s,the tensile strength is 409.9 MPa and the elongation is 12.96%,reaching the maximum value.