Effect Of Equal Channel Angular Pressing On Microstructure And Properties Of 2A12 Aluminum Alloy And High Pure Al

Equal Channel Angular Pressing (ECAP) is one kind of promising severe plastic deformation methods, which can produce ultra fine and even nano scale grains.An important advantage of ECAP is that it can obtain pure shear deformation by multi-pass pressing without changing samples’ shape, refine grains and improve mechanical properties of material.A large amount of energy accumulating by ECAP makes the refined material thermodynamics instability. Therefore, this paper firstly investgates the thermostability of 2A12 aluminum alloy by ECAP after annealing at 100℃,150℃ and 200℃ for 1h, respectively. According to the basic theory of ECAP, there are various factors which can influence grain refinement of ECAP technology, such as mold structure, pressing pass, pressing temperature and process route. The influence of process route on microstructure and properties was studied in this paper. We design a new process route X combined with grain refinement theory. The cross-section shape dimension Φ15mm of high pure Al was used as the experimental material to do ECAP experiment. In ECAP the new process route and the traditional route BC were used. The polarized light organization, hardness and TEM organization of the samples were observed to make comparative analysis. Finally, we propose a new method combined multiple forging with ECAP for the billet of strip shape. The samples after multiple forging were used to do ECAP in route A and route C. We analyze its microstruture contrastively.Thermostability experimental results show that a large amount of energy accumulating by ECAP in route BC makes 2A12 aluminum alloy separate out θ phase when annealing at 150℃, while θ phase separated out at 200℃ in route 135 because its thermostability is better than route BC. With the increase of annealing temperature the hardness of samples in route 135 for different passes began to decline after a modest rise. The hardness of samples in route BC for different passes declined with the increase of annealing temperature. So the thermostability of route 135 is better than route BC.Round pieces experimental results show that the effect of grain refinement in route X designed was obvious, and it is better than that of route BC. The billet of strip shape experimental results show that the combination of ECAP and MDF reduced the pressing pass, even improve the deformation uniformity. The grain size of route A after second pass was smaller. The grain size of route C after third pass was smaller. Their grain size is similar after fourth pass, while the grain size of route C was more uniform. Therefore route C is better than route A generally.