THE EFFECT OF STRESS ON GRAIN-BOUNDARY GROOVING

A theory of the effect of stress on grain boundary (GB) grooving is developed under the assumptions of matter transport by surface and GB diffusion, and steady-state diffusion in the GB. A uniaxial stress normal to a planar GB induces a flux at the GB root, out of (in to) the boundary for compression (tension), proportional to the stress. The corresponding solution is joined to that for thermal grooving at the surface using the continuity of chemical potential and of flux at the groove root. For planar geometry and small slopes, grooving under stress is described by a superposition of the solution for stress-free grooving and that generated by the stress-induced flux with no groove. Limits of the approximations are discussed. The analysis predicts an acceleration of grooving by a tensile stress and offers the possibility of an absolute measurement of the GB diffusion coefficient for mass transport.