Diffusion-Drift Effect on Grain Boundary Grooving

摘要

Diffusion-drift effect is a fast diffusion penetration along grain boundaries (GB) due to the concentration gradient and the force causing drift with the rate V = const. Earlier the problem was discussed with the use of two dimensionless parameters ?-(4Dt)~(1/2)/δ and γ = Vt/ (4D_bt~(1/2) where D and D_b are the coefficients of bulk and GB diffusion, δ is GB width and t is the lime. In this paper a fresh portion of the solution is introduced into the denominator of β which is now equal to sδ, where s is the segregation coefficient: s = C_b/C, where C and C_b are the bulk and GB concentrations of diffusant. The numerical solutions of the problem are obtained for different β and γ. These solutions are applied to the process of GB grooving. The region is limited of such β, γ-values when the drift flux predominates and the long step exists at GB solute concentration profiles. The main contradictions of the problem are discussed. If the drift effect is significant it may probably explain a cracks formation without external stresses.