Study On Deformation Behavior And Microstructure Of Al-Zn-Mg-Cu Alloy By Equal Channel Double Angular Pressing

Al-Zn-Mg-Cu alloy has a wide range of applications in ships,military equipment,nuclear industry and bridges due to its high hardness,specific strength,toughness,and good corrosion resistance.The equal channel angular pressing?ECAP?is an effective method to refine grain and prepare ultrafine crystalline materials.Because of the serious internal angle wear and breakage of the punch,the traditional ECAP die??=90°,?=37°?has a serious internal angle wear.Therefore,in this paper,a new ECAP die for the traditional 90°angle is improved,and a new type of equal channel double angle extrusion?ECDAP?die is proposed,which transforms the shear deformation effect of90°to the cumulative deformation of double 135°shear angle.In this paper,the DEFORM-3D finite element simulation software is used to analyze the ECDAP deformation process of Al-Zn-Mg-Cu alloy in detail,and the deformation process is compared with the 90°and 135°ECAP deformation process.The results show that,during the process of ECDAP deformation,the average strain value of the billet after the first turning angle is 0.471,the average strain value is 0.935 after the second rotation angle,and the cumulative strain value is close to the theoretical value,and the deformation effect of"one squeeze,twice shear"is realized.After ECDAP,the equivalent change value of the sample is close to 90°ECAP,but the inner angle of the ECDAP is less than that of the 90°ECAP die,and the uneven force of the punch and the deformation of the specimen are improved.A physical grid sample and ECDAP with different deformation parameters under Bc path are carried out,and ECDAP samples with large section size are prepared.Based on optical microscope?OM?,microhardness tester,X ray diffraction analyzer?XRD?and room temperature tensile test,the microstructure and mechanical properties of the alloy after ECDAP deformation are investigated.The results show that with the increase of deformation passes,the crystallite size of the alloy decreases,and the microstrain increases,resulting in a remarkable grain refinement effect.After four passes,the dislocation density of the alloy also increases by one order,from the initial 3.64×10¹²m^-22 to the four pass 5.13×10¹33 m^-2.After one ECDAP deformation,the tensile strength and elongation of the alloy increase obviously,reaching 346 MPa and 18.4%respectively.After heat treatment,the tensile strength of the 1-4 pass samples increase significantly,and the four pass reaches 610.3 MPa.