| Al-Cu-Mg alloy has the advantages of high specific strength,high specific stiffness,good corrosion resistance,etc.,and is widely used in weapon equipment,aerospace,rail transit,and other fields.Compared with the traditional process,the material prepared by spray forming has the advantages of fine grains,uniform structure,low degree of segregation,and good mechanical properties.At present,there are little researches on the microstructure and mechanical properties of spray-formed Al-Cu-Mg extruded alloys by severe plastic deformation,therefore,studying the microstructure characteristics and mechanical properties of severe plastic deformation spray-formed Al-Cu-Mg alloys and clarifying the relationship between strain and strain rate and microstructure properties have important theoretical significance and application value for the development of high-strength and high-toughness special aluminum alloy materials.In this paper,a series of rapid cold punching and hot deformation experiments with different strains and strain rates were carried out for spray-formed Al-Cu-Mg extruded alloy.The effects of strain and strain rate on the microstructure and mechanical properties of the alloy were investigated by means of various testing and characterization methods.The main research content includes the following three aspects:(1)The Gleeble-3180 thermal simulator was used to study the flow stress behavior of the spray-formed Al-Cu-Mg extruded alloy under different deformation conditions(deformation temperature 300-450,strain rate 0.01-10 s-1);Based on the constitutive equation of the hyperbolic sine function and the Z parameter to describe the high-temperature deformation behavior of the spray-formed Al-Cu-Mg extruded alloy;using the dynamic material model to establish 2D processing maps and 3D power dissipation maps to analyze the effect of strain and strain rate on the hot compression of the alloy,optimize the hot deformation process parameters of the alloy,and provide a theoretical basis for subsequent plastic forming.The results show that in hot compression deformation,with the increase of strain,the instability zone gradually expands to the middle and low strain rate regions.Dynamic recovery occurs at low temperature and high strain rate,and dynamic recrystallization occurs at high temperature and low strain rate.The region with a temperature range of 400-450°C and a strain rate of 0.01-0.08 s-1 has better processing performance.(2)The spray-formed Al-Cu-Mg extruded alloy was subjected to rapid cold punching deformation with different strains.TEM,SEM and XRD were used to analyze the evolution of the second phase of the alloy under different strain conditions and reveal the effect of strain on the microstructure and mechanical properties of spray-formed Al-Cu-Mg alloys prepared by rapid cold punching.Studies have shown that the dislocation density in the alloy increases with the increase of strain.When the strain increases to 0.6,the number of precipitates in the alloy increases significantly.When the strain increases to 0.9,the number of precipitates is the largest.With the increase of strain,the stress of the alloy increases continuously,and the hardness increases from 80.1 HV to 133.2 HV.(3)The effect of strain rate on the mechanical properties of Al-Cu-Mg alloy prepared by rapid cold punching and hot rolling by severe plastic deformation is investigated.TEM was used to analyze the changes in the microstructure of the alloy in the hot rolled state with severe plastic deformation,and the fracture and re-dissolution mechanism of the S?phase of spray-formed Al-Cu-Mg extruded alloy under hot rolling at different strain rates was discussed.The strengthening and toughening mechanisms of Al-Cu-Mg alloy under severe plastic deformation at different strain rates are clarified.Research has shown that S?phases of spray-formed Al-Cu-Mg extruded alloy are distorted,broken,and resolved to a certain extent during hot rolling.With the increase of strain rate,the number of precipitates and dislocation density decrease,the tensile strength decreased from 492.45 MPa to 427.63 MPa.During the rapid cold punching process,the strain rate has little effect on the mechanical properties of the spray-formed Al-Cu-Mg extruded alloy. |
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