https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Inoue-ActaMater00-Stabilization%20of%20metallic%20supercooled%20liquid%20and%20bulk%20amorphous%20alloys.pdf

Stabilization of metallic supercooled liquid and bulk amorphous alloys

Influence of predeformation and agEing of an Al–Zn–Mg alloy—II. Modeling of precipitation kinetics and yield stress

Theory of Thermal Conductivity of Solids at Low Temperatures

Based on recent experimental observations a realistic model of the evolution of the surface profile of persistent slip bands (PSBs) in fatigued metals is proposed. An essential feature of the model is the production of vacancies by the annihilation of edge dislocations which, combined with irreversible slip processes, leads to an elongation of the PSB parallel to the active slip vector. It is shown that a net extrusion forms rather rapidly. The growth processes and their dependence on temperature are discussed in detail. It is proposed that cracks initiate at the surface steps at the PSB–matrix interface and, at a later stage, also at the notch-peak profile from the random slip processes.

A model of extrusions and intrusions in fatigued metals I. Point-defect production and the growth of extrusions

Influence of predeformation on ageing in an Al–Zn–Mg alloy—I. Microstructure evolution and mechanical properties

The kinetic theory for the rate of stress‐assisted precipitation on dislocations is re‐examined in order to extend the work of Cottrell and Bilby. Two approximate expressions are used for the elastic interaction between a solute atom and edge and screw dislocations: V=−A sinθ/r and V=−B/r, respectively. The resulting partial differential diffusion equations are integrated numerically to get the time‐dependent rate of precipitation on an isolated dislocation. These results are used to calculate the short‐time part of the precipitation curve for an array of dislocations. Exact steady‐state solutions to the diffusion equations are derived for both interactions and are used with a variational procedure to establish the long‐time part of the curve for a regular array. For very short times the precipitated fraction W is proportional to t⅔ as derived by Cottrell and Bilby, but this result is not accurate over the range of t during which most of the precipitation occurs. The long‐time part of the curve is given a...

Stress‐Assisted Precipitation on Dislocations

Diffusion‐limited precipitation rates are calculated, using theoretical methods derived previously, for systems of precipitate particles which may change shape as they grow. General formulas are presented, including suitable short‐ and long‐time approximations. Explicit growth laws are derived for systems in which particles are disks and rods subjected to various constraints. The growth exponent n in the short‐time approximation is found to be 2 for disks of constant thickness. Rods of constant radius that capture atoms only near their ends have n=1. Both disks and rods of constant ratio of their long and short dimensions have n=3/2. These values contrast with growth laws suggested by Wert and Zener for disks and rods, for which they found n=5/2 and 2, respectively. It is shown that growth conditions at the edge of a growing particle are not constant in diffusion‐limited circumstances if the entire surface of the particle acts as a sink.

Frank S. Ham

Papers

Stress‐Assisted Precipitation on Dislocations

Diffusion‐Limited Growth of Precipitate Particles