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Grain-boundary sliding and diffusion creep in polycrystalline solids

1971; Taylor & Francis; Volume: 23; Issue: 182 Linguagem: Inglês

10.1080/14786437108216383

0031-8086

R. N. Stevens,

Rock Mechanics and Modeling

Abstract The diffusion creep of polycrystalline materials must be accompanied by grain-boundary sliding in order that material continuity be preserved. Since both grain-boundary sliding and the addition of atoms to a boundary between two grains result in a relative translation of the grains, it is possible to regard the material as deforming by the motion of its constituent crystals. A detailed analysis of the grain-boundary sliding occurring during diffusion creep in simple tension has been made, based on this point of view. It is concluded that the relative velocities of displacement by grain-boundary sliding and by diffusion at a particular point on a grain boundary are fixed by the geometry of the grains. The relationship between these relative displacement velocities is found and it is concluded that sliding is occurring at most grain boundaries in a normal polyerystalline material undergoing diffusion creep. It is also shown that sliding on most boundaries makes a positive contribution to specimen strain. Equations are developed for the contribution of both sliding and diffusion to the total strain. These can be evaluated exactly for idealized models in which all the grains are identical. It is shown that grain-boundary sliding contributes over 60% of the total strain for materials with equiaxed grains of uniform size.