Grain-refining mechanism of ECAP and its effect on microstructures and mechanical properties of pure Al

Experiments were conducted to investigate the microstructures and mechanical properties of pure Al by equal channel angular pressing (ECAP) in which three kinds of route was employed. It was found that for the φ=120° die, effectiveness of ECAP route A, Bc and C in grain refinement were more inferior to each other respectively. The microstructure of the specimens after 6 passes of ECAP by route Bc was consisted of the equiaxed grains, whereas the microstructures by route A and C was consisted of elongated grains, and the average grains sizes under three routes were less than lμm. Accordingly, the effectiveness of three routes in improving strength was in descending order from route A to route C, during ECAP the relationship of δ_0.2 and grain sizes obey Hall-petch relationship. Grain-refining strengthening is dominant strengthening mechanism in ECAPed pure Al, and the formation of refine grains during ECAP was simply explained.