DIFFUSION-INDUCED BENDING OF THIN SHEET COUPLES - THEORY AND EXPERIMENTS IN TI-ZR SYSTEM

Numerical and analytical calculations of concentration and stress dist ributions of thin-sheet diffusion couples have been carried our as wel l as the time dependence of the Kirkendall shift, sk, and the curvatur e has also been determined. It is shown that the concentration distrib ution is not sensitive to the boundary conditions (bent and planar, co nstrained, samples) and is influenced mainly by the feeding back effec ts of stresses (described by the stress term in the generalized diffus ion potential) only. The stress distributions obviously are different for bent and planar samples and the effect of cutting off, caused by t he dislocation glide, is also illustrated. It is found that the Kirken dall shift follows the parabolic law only in high creep rate limit. Fo r intermediate creep rates, as a Function of the time, t, a change of the slope of the x(k)(r) Function is expected due to the stress develo pment and relaxation. It is shown that the curvature of samples, cause d by the diffusion stresses, is proportional to the annealing time and the difference of the intrinsic diffusion coefficients in a wide rang e of input parameters. By the example of experiments on Ti-Zr thin-she et diffusion couples it was illustrated that the theoretical results a re in good agreement with the measurements. Copyright (C) 1996 Acta Me tallurgica Inc.