| Al-Zn-Mg-Cu alloy with high strength,high toughness,good diffusion,low density and great potential for weight loss,as a new generation of high-quality aluminum alloy structure,so in ordnance equipment,aerospace,nuclear industry,ships and bridges and other fields have its wide range of applications.It is considered the most likely alternative to steel,iron and non-ferrous materials.In this paper,a new type of Al-Zn-Mg-Cu alloy（7A60）was used to ECAP experiment at different process parameters（deformation temperature and deformation pass）.The microstructure evolution and mechanical properties of Al-Zn-Mg-Cu alloys under different deformation conditions were investigated by means of various analytical tests（OM,SEM,TEM,XRD,tensile strength and hardness）and theoretical calculations.The results show that the effect of grain size reduction on isostatic deformation is obvious.From the initial 9.86μm to about 4μm 1μm,the dislocation density increases remarkably,and the anisotropy of the alloy decreases and the microstructure homogeneity increases.The most important secondary phase of Al-Zn-Mg-Cu alloy is?（MgZn2）,with the increase of the pass,the microstructure of the smaller precipitates coarsening from the initial state of 53.02nm coarsening to 4passes of 410nm.With the increase of the deformation,the secondary phase is dissolved into the aluminum matrix to form supersaturated solid solution,the concentration of vacancies in the matrix increases,and the vacancy concentration in the tissue reaches to the alloy melting point concentration after one pass of equal diameter angular press.At the same time,a lot of dislocations and other defects are generated inside the substrate.The solute atoms tend to combine with vacancies to form vacancy-solute complex,which diffuses inside the matrix and segregates at the grain boundaries and dislocations to form a coarser second phase.In addition,the mechanical properties of deformed specimens were tested at room temperature.The effects of process parameters of ECAP on the tensile strength and elongation of Al-Zn-Mg-Cu alloys were investigated.At the same time,scanning electron microscopy（SEM）was used to scan the fracture surface to study the fracture morphology and fracture mechanism.The results show that the properties of the alloy after ECAP deformation are greatly improved,the initial strength is 280Mpa,the maximum tensile strength reaches 395Mpa after the ECAP,the growth rate reaches41%.The elongation of the initial state alloy is 0.24,the maximum elongation after extrusion is 0.28,the growth rate reached 16.6%.The Hall-Petch equation is used to quantitatively calculate the alloy strengthening.The results show that the fine grain strengthening and dislocation strengthening increase with the increase of deformation pass,but they do not play a significant role in the whole strengthening effect.The dispersion strengthening plays a leading role.The stress corrosion resistance of T6-treated samples after ECAP was measured.The effects of different deformation parameters（deformation temperature and deformation pass）on the stress corrosion resistance of the alloy were analyzed by open circuit potential,polarization curve and impedance spectroscopy impact.The analysis shows that with the increase of deformation pass,the stress corrosion resistance of the alloy increases.With the decrease of deformation temperature,the stress corrosion resistance of the alloy decreases. |
