Characterization of mechanical properties of aluminum 3003, 6061 and 7075 subjected to equal channel angular extrusion

Abstract

Equal channel angular extrusion (ECAE) is a novel method for introducing large amounts of simple shear into materials. In comparison with conventional deformation processes, ECAE has a number of significant advantages. The two most important ones being: very large and uniform deformation can be induced in a material without a reduction in work piece size, and the orientation of the billet can be altered to develop specific textures in materials. This innovative technique (ECAE) is applied to I"xl"x6" billets of aluminum alloys 3003, 6061 and 7075 and copper 101, and the effects of processing parameters (number of passes, route. deformation temperature and strain rate) on the mechanical properties (and resistivity for copper 101) has been studied. The mechanical properties (hardness and strength) obtained in these materials is superior to those achieved in equivalent sizes of materials processed by conventional methods. In aluminum 3003, given four extrusion passes, with the billet rotated 180' between successive passes, the most stable microstructure is achieved. Whereas, a In aluminum 6061, significant differences in hardness and strength were developed between pre extrusion peak aged and overaged materials. For peak aged material, increasing the number of passes beyond four does not significantly increase the hardness, whereas lowering the deformation temperature enhances hardness. For overaged aluminum 6061, these results are reversed. The hardness of aluminum 7075 is not significantly affected by changes in number of passes, deformation temperature and extrusion strain rate. On the other hand, the hardness of specimens rotated 90' between successive passes is significantly higher than specimens rotated 180'. In general, the hardness decreases with post extrusion annealing till 300'C, beyond which it increases.