The Speed, Grain Boundary Morphology, and Composition Changes Resulting from DIGM

Published

February 19, 2017

Author(s)

John W. Cahn, C M. Elliott, P C. Fife, O Penrose

Abstract

We use the equations for steady-state diffusion-induced grain boundary motion (DIGM), derived from our phase-field model, [17] to predict the grain boundary morphology and speed of DIGM, as well as the resulting compositions profiles, when the specimen thickness, and the composition change imposed at the surface are varied. The results display strong effects from grain boundary grooving, which slows DIGM and stops it unless there is a threshold composition change that depends on specimen thickness. At this threshold the steady-state speed jumps discontinuously to a non-zero value. The strong interplay of composition change imposed at the specimen surface, grooving, and specimen thickness produce three major regimes with several subcases: no DIGM, motion of boundaries that traverse the specimen, and motion of grain boundaries near the surfaces only. For each case we derive the conditions that produce it. Grain boundary curvature provides a driving force, which at times opposes the DIGM driving force almost fully, reducing the DIGM speed by orders of magnitude. At other times curvature compensates for the variations in DIGM driving force due to composition gradients along the grain boundary, providing the driving force for motion to the portions of the grain boundary where there is little assistance from diffusion.

Citation

Acta Materialia

Pub Type

Journals

Keywords

coherency stress free boundary problem, diffusion, Diffusion induced grain boundary motion, grain boundaries, morphology

Citation

Cahn, J. , Elliott, C. , Fife, P. and Penrose, O. (2017), The Speed, Grain Boundary Morphology, and Composition Changes Resulting from DIGM, Acta Materialia (Accessed April 19, 2024)