Microstructure And Properties Of Al-Zn-Mg-Cu Alloy Based On Equal Channel Angular Dual-directional Extrusion

As one of the effective methods to refine grains and improve the comprehensive properties of materials,the severe plastic deformation(SPD)method has the advantages of low cost and simple operation.Among them,equal channel angular pressing(ECAP),as a typical representative of large plastic deformation,is widely used to obtain bulk high-performance materials with fine grains,uniform structure and large size.However,the material with high deformation resistance tends to crack when it passes through the corner of the die,and the punch will also appear partial load.Dual equal channel angular pressing(DECAP)is a new large plastic deformation process which developed on the basis of ECAP.It can achieve the severe plastic deformation of materials quickly,solve the problem of left-right asymmetry of specimen and avoid the breakage of the punch,but this extrusion method still has the problem of inhomogeneity deformation.Based on this,the equal channel angular dual extrusion(ECADE)method is proposed.The deformation process of ECADE process is studied by combining finite element simulation with physical experiment.The advantages and disadvantages of the three processes are compared and analyzed in detail.The results show that severe shear deformation can be achieved by multi-pass ECADE deformation with different paths,but the uniformity of deformation is different.After four passes of B-path deformation,the coefficient of non-uniformity of deformation decreases to 0.94,and the proportion of uniform deformation area reaches 86%.Meanwhile,the uniformity of B-path of ECADE process is always better than that of ECAP and DECAP process under the same pass n?mber.In this study,taking Al-Zn-Mg-Cu alloy as research object,the ECADE process deformation die was designed,and the physical experiments were carried out in different conditions of ECADE.The effect of ECADE process on the structure and properties of Al-Zn-Mg-Cu alloy was investigated by observing the microstructure,macro-texture testing and mechanical properties testing of the deformed specimens.Finally,the deformed specimens were treated by solution ageing.The results show that the properties of the deformed specimens can be further improved after heat treatment.Microstructure observation results show that ECADE process can significantly refine the grain size,the average grain size of 1 pass deformed specimen after solution aging treatment is less than 10 ?m.The results of macro-texture observation show that after four passes of deformation,the orientation of grain [1 0 0] in path A is nearly parallel to that in plane Z,and part of grain {1 0 0} in path B is perpendicular to that in plane Z.After heat treatment of deformed specimens,the texture types of the two paths tend to be the same.The mechanical properties test showed that the tensile strength of ECADE specimens increased by 16.5% in the severe deformation zone after first pass deformation,and the increase of the tensile strength of B path exceeded that of a path under the same pass,but with the increase of pass,the increase of the tensile strength decreased in turn.After solution aging treatment,the tensile properties of the specimens with the value of 704 Mpa increased by 106.4% compared to the original specimens after one pass deformation.Similarly,the tensile properties of the specimens could not be further improved with the increase of passes.