RESUMEN
An ultrafine-grained EN AW 6082 aluminum alloy was prepared by continuous serve plastic deformation (i.e., thermo-mechanical equal channel angular pressing (ECAP)-Conform process). A miniaturized tensile testing technique was used for estimating local mechanical properties with the aim to reveal the inhomogeneity of elastic and plastic properties in a workpiece volume. These inhomogeneities may appear due to the irregular shear strain distribution in a Conformed wire. Miniaturized samples for tensile testing were cut from the Conformed workpiece. Elongation of miniaturized samples was measured with a 2D digital image correlation technique as the optical extensometer. Tensile test characteristics, such as the yield strength and ultimate tensile strength, were consequently compared with results of conventional and hardness tests. The microstructure of Conformed bars was studied in the cross-section perpendicular and parallel to the extrusion direction using scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) analysis. The microstructure of samples exhibits pronounced inhomogeneity, which is reflected by the hardness and tensile test results. Estimated distinctions between peripheral and central parts of the Conformed wires are probably a consequence of the significant strain differences realized in the upper and bottom wire parts.
RESUMEN
This work concerns mechanical properties in relation to microstructural changes in hardenable EN AW-2024 aluminium alloy in wrought and heat treated condition. The treated material benefits from synergistic effects of hardening mechanisms. Grain boundary strengthening and work hardening were activated in this material by rotary swaging. Rotary swaging is a method which shows great promise for industrial use. Precipitation hardening was achieved thanks to the material's age hardening ability. First, the material was artificially-aged in a furnace at 140-180 °C. Second, natural ageing was used. Mechanical properties of the as-treated material were tested and microstructural processes were explored using electron microscopy and differential scanning calorimetry. The treatment route which delivered the best results was as follows: solution annealing 500 °C/1 h + water cooling + rotary swaging + artificial ageing 160 °C/21 h. This led to a yield strength close to 640 MPa, and ultimate strength above 660 MPa, and elongation of 8%. Electron backscatter diffraction observation revealed that in this condition, the ratio of Low-angle to High-angle grain boundaries is 80:20. The microstructure contains both T-phase in the interior of grains, whose particles are normally oval-shaped, and S-phase, which is present in two shapes: small oval particles or coherent needles aligned to <100> direction.