MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HIGH-PURITY ALUMINUM DEFORMED WITH EQUAL-CHANNEL ANGULAR PRESSING

Annealed high-purity (99.99 %) aluminum was processed with equal-channel angular pressing (ECAP) via the Bc route making 1-8 passes at room temperature. The microstructure evolution of the materials processed at different pass numbers was observed and analyzed with EBSD; the influence of the ECAP-deformation pass number on the mechanical properties of high-purity aluminum was studied through mechanical-property tests. The result showed that the subgrain-boundary misorientation and the fraction of high-angle boundaries increased with an increased number of pressing passes. Dynamic recrystallization occurred and small equiaxed grains began to form after 4 passes; grains were refined to 4.0 mu m after 8 passes. The microhardness and tensile strength were obviously improved, while the elongation decreased. However, the tensile fracture remained a typical ductile fracture. The thermal stability of high-purity aluminum decreased after being annealed at 200 degrees C.