| Today, with the rapid development of aerospace, armament and vehicle, the need for high performance metal is keeping on increasing, especially for nano-materials with high specific strength. However, to prepare nano-structure materials with high specific strength and excellent obdurability is a difficult problem for scientists in world, and it is also one of the most drastically competitive fields for every country. It is very important to evaluate the relationship between microstructure and mechanical property of nanostructure material, especially to obtain the relationship through an accurate mathematic model.Severe plastic deformation is an efficient route to prepare ultra-fine grained and nano-structure metal materials. ECAP (equal-channel angular pressing) and correlated large-deformation technology is a promising method for industrial application. In the paper,2024 Al was used to obtain super-high specific strength and ultra-fine grain structure. The strengthening mechanism basing on microstructure level and the promising process were also investigated. Detail research contents and some innovative conclusions are listed as follows:(1) The effects of parameters, such as inner arc radius, channel angle, friction coefficient and extrusion velocity on ECAP deformation, strain value, strain distribution and temperature rising have been analyzed by finite element simulation software. When the materials are subjected to ECAP, the cracks occur or not can be judged by the relationship that the maximum shear stress is less than the shear strength of materials. This provides a theoretical guidance and research method for ECAP process of low plastic materials, mould design and pretreatment process. To avoid overaging and recrystallization, the concept of safe parameter region for large strain technology was put forward. This offers theoretical elements for integrating several strengthening processes to prepare super-high strength material.(2) It is first time to combine the technical route of enhanced solid solution—Severe plastic deformation (ECAP)—artificial ageing treatment at low temperature for preparing high specific strength and well ductile 2024 Al. This provides a new promising route for producing high specific strength and well ductile nano-structure 2024 Al which has wide application perspective. The results show that yield strength of 2024 Al is increased from about 460 MPa to about 610 MPa and the elongation remains about 13%. Micro-hardness test and XRD spectra indicate that artificial ageing treatment at low temperature can further improve the mechanical property of the solid solution strengthening aluminum alloy after ECAP process. According to quantitative calculation basing on the relationship between material strength and microstructure, the dislocation strengthening due to ECAP process accounts for about 62.2% in total.(3) To quantitatively investigate the relationship between strength and microstructure, overaging 2024 Al was processed with several ECAP processes and large strain compressive process at liquid nitrogen temperature. The result shows that yield strength of alloy mainly come from large angle grain boundary strengthening, dislocation strengthening, sub-boundary strengthening and friction stress of lattice, while the sub-boundary strengthening should be further discussed. The results indicate that the dislocation introduced by liquid nitrogen temperature compressive deformation has slight effect on the strength. Continuous severe plastic deformation can only put mild effect on the strength and hardness of 2024 Al with ultra-fine grain. This may be due to that dislocation moves to sub-boundary by high density face defect, and then the dislocation can not play effect on dislocation strength, leading to dynamic recovery.High strength aluminum alloy should be prepared by the pinning efficiency which comes from the dislocation due to the tiny precipitation of alloy elements during large strain process, leading to the accumulation of high density dislocation within material.(4) The continuous ECA technology which drived by several pairs of wheels was creatively provided to solve the limitation of ECAP. Through emulational simulation, the effect rules of the driving wheel number, friction coefficient between driving wheel and workpiece, the rotating speed of driving wheels on the restraining skidding of workpiece, torque of driving wheels and energy consumption are established, and the technical parameters are also optimized. Hence, the technology foundation and theoretical basis of ECA are established.In this paper, the preparation and effect factors of block nanostructure material by equal-channel angular large deformation technology were studied. The research results may provide theoretical basis and technology route for preparing super-high strength aluminum alloy, and the technology foundation of new efficient continuous ECA large deformation technology is established.
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