Plastic Deformation Of Pure Aluminum By Equal Channel Angular Processing

Equal Channel Angular Processing (ECAP) technique has been proved to be an effective method for the fabrication of various bulk ultrafine-grained materials 1990s.The sample can obtain micron or nanostructured microstructure by subjected to intense plastic straining in a die for ECAP. Compared with other method of preparing bulk nanostructured materials (such as vapor condensation, ball milling), ECAP method is in possession of several unique advantages. For example, ECAP method results in overcoming a number of difficulties connected with residual porosity in compacted samples, impurities from ball milling, processing large-scale samples and practical application of the given materials. The unique properties in ECAP ed materials play significant performance in both practical application and academic research.Equal channel angular pressing technology (ECAP) provides an effective procedure for obtaining the bulk sub-micrometer or nanometer scale materials by sever plastic deformation. According to the fundamental theories and the latest research progress, we analyze systematically the influences on microstructures and properties of the ultra-fine grained materials caused by technologic parameters such as structure and dimensions of ECAP dies, the number of pressing ,the routes of ECAP, the velocities: temperature and the friction states of the ECAP.The pure aluminum was used as the experimental object of ECAP experiment. By the experiment the optimizing technologic parameters were determined and the different corresponding die was designed and manufactured. Deformation behavior of the ECAP was researched. Simulation results illustrate that according to the variation of load with time, ECAP process in simple structure can be divided into three steps: rapid load increase; steady load; load decrease. The load value in complex structure always increases with time increase. By the experiment of etched-grids, the process of materials plastic deformation was known. In the process of ECAP, the strain state of sample in different part is different and occurs to uneven formation. But complex structure,s plastic formation process is even than simple structure , s one .In fact the characteration of materials liquid change and the distribution of sample deformation are depended on the friction force and the sample,s processing method.Based on the new research result of ECAP deformation in world, the influence of different parameters on microstructure grain refiner was investigated. In this experiment, the pure aluminum was deformed in the die for ECAP. The course of grain refiner shear characteristic, microstructure evolution and property characteristic of the pure aluminum were researched by optical microscope and scan electronic microscope. Finally, the factors affecting grain refinement were discussed in detail.