Back Pressure Equal Channel Angular Pressing of Consolidate Pure Al Particles

In this study, pure aluminum particles were successfully consolidated to fully dense bulk material by back pressure equal channel angular pressing (BE-ECAP) at room temperature, the evolutions of microstructure and densification mechanism were systematically investigated using an FEI-TECNAI G20 transmission electron microscope (TEM) operating at 200kV, FEI field-emission scanning electron microscope (FE-SEM) and hardness testing. The results indicated that the strong bulk materials from particles were successfully produced. After 4 BE-ECAP passes, the present samples show finer grains with the average grain size of ~10μm, the density of the sample was considerably higher compared to those of the materials that had undergone ECAP without back pressure, and was approach to the theoretical density of pure Al. This was related to the combination of hydrostatic pressure, shear deformation and strain accumulation. The mechanisms of grain refinement was the dislocation generated inside grains moves towards the grain boundary continuously, and accumulates, tangles annihilates at the grain boundaries, which resulting in the grains continuously fragmented and refined.