The plastic deformation of polycrystals I. Aluminium between room temperature and 400°C

Publisher Website
Google Scholar
Abstract
The tensile flow stressσ∊ has been studied for super-pure and commercial aluminium and for an Al-21/4% Mg alloy in relation to strain, grain size d, subgrain or cell size and dislocation density ρ. At room temperature and 200°C, the flow stress depends on both ρ1/2 and d −1/2. This is interpreted an evidedce of a requirement inσe that slip can be transmitted across a grain boundary. There is extensive dislocation annihilation during deformation at these two temperatures, particularly in the two aluminiums and particularly in fine grains. The behaviour of the commercial aluminium is unusual. At room temperature, the retained ρ is higher in coarse than in fine grains. However, the flow stress remains higher in the fine grains because of the slip transmission requirement. At 200°C, the dislocation density is so much higher in the coarse grains that the flow stress is also higher. At 400°C, most of the dislocations are annihilated and sharp subgrains form with planar network boundaries. It is proposed that the flow stress is determined by the boundary network and the size of the subgrains rather than by the three-dimensional dislocation network within the subgrains.