Effect of grain size on tensile behaviour of a submicron grained Al-3 wt-%Mg alloy produced by severe deformation

Equal channel angular extrusion has been used to deform an Al-3 wt-%Mg allo y to an effective strain of 10, resulting in a 0.2 pm grain size. In the as deformed condition the yield strength was increased to similar to 500 MPa. During annealing the grain structure coarsened uniformly and the yield str ess was found to follow the Hall-Fetch relationship, even in the submicron range. There was an abrupt transition in elongation at a grain size of simi lar to0.5 mum. Samples with smaller grain sizes showed no uniform elongatio n and limited ductility. For slightly greater grain sizes there was only a relatively small reduction in elongation, compared to a coarse grained mate rial, while the yield stress was still increased by a factor of over four. Reducing the grain size to the submicron range led to far higher Luders str ains than are normally observed in Al-Mg alloys. MST/4770.