Z. Chen, A. V. Kazantzis, J. T. M. De Hosson, University of Groningen and the Netherlands Institute for Metals Reseach, Groningen, Netherlands
Two coarse-grained Al alloys AA5182 with as-received grain sizes 19 and 34 μm have been evaluated with respect to their superplastic properties along the rolling direction, perpendicular to the rolling direction and at 45° to the rolling direction. The elongation to failure at 45° was larger than that deformed along the rolling direction, whereas, that of the specimens perpendicularly to the rolling direction was consistently larger than of 300% at temperatures between 425 and 450oC and at strain rates 10-2 s-1.The relatively lower elongation to failure of the specimens (by 20 or 30% nominal strain) tested along the rolling direction was directly related to the fraction of the grain boundaries along the direction of the applied stress. The final annealing of the rolled as received material resulted in slightly non-equiaxed grains with the larger axis along the rolling direction. As a result the number of the grain boundaries at 45° and perpendicular to the rolling direction increased.
Even though the flow stress recorded at 0.05 and 0.1 nominal strain did not exhibit notable systematic variations the larger fraction of the grain boundaries oriented perpendicular or almost perpendicular to the applied easier appeared to have facilitated easier recovery and grain refinement. As a result larger elongations to failure were recorded.
Summary: This paper report the anisotropic superplasticity of Aluminum alloy AA5182 provided by Aleris and Corus, derived from the uniaxial tensile testing experiments. The AA5182 materials have coarse grain size of 19µm and 34µm, thus the deformation were performed at high temperature of 450°C in the high strain rate region from 10^-3 to 10^-1 s-1. The anisotropic superplasticity was studied on the specimens machined along, perpendicular, and 45° oriented to the rolling direction. Different maximum enlongation to failure were compared, while the inequiaxial grain orientation was taken into account. And the microstructure characterizations were obtained by means of SEM, EDX, and Electron Backscatter Diffraction methods.
