Solid solution hardening of metal crystals

Abstract

The dependence of the yield stress of binary solid solution crystals on temperature and alloy concentration is explained in terms of a simple model in which the breakaway of dislocations from short rows of pinning points is rate determining. With an assumed binding energy of about 0·01 ev between dislocations and zinc atoms the calculated yield stress of α-brass single crystals agrees quantitatively with measured values in the range 0-400°K. The yield stress of dilute solid solutions, particularly iron alloys, and a possible bearing of the present theory on the problem of the temperature dependence of the Peierls stress, are discussed briefly.

Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters

“…The unit activation process of yielding in the KPN model [5][6][7] involves the stress-assisted, thermally-activated detachment of edge-dislocation segments from short rows of closely spaced solute-atom pinning points. This occurs in a manner similar to the kink-pair mode of escape of screw dislocations from Peierls valleys [17] in nominally pure crystals with high intrinsic lattice friction.…”

“…Now the activation energy W (τ) for the formation of the arc ACB (Fig. 1), taking AC and BC to be approximately straight lines, is given by [7] …”

“…In his paper, Feltham [7] [4] so that Eq. (3) with these values of ν and ν leads to the yield criterion…”

“…In fact in the KPN model [5][6][7] the parameter U 1/2 , which is the binding energy per interatomic spacing along the edge-dislocation segment pinned with solute atoms, or the parameter W , which is the total binding energy of edge-dislocation segment of length L pinned with N solute atoms, is a measure of the overall or cumulative effect of all the factors referred to above. Nevertheless we shall now examine any possible correlation of the critical solute concentration with the electron-to-atom ratio / for the binary alloys referred to in Fig.…”

“…The kink-pair nucleation (KPN) model of plastic flow in solid-solution crystals [5,6], which is essentially a revised and enlarged version of one initially proposed by Feltham [7], has not only satisfactorily accounted for the SSH features noted above (e.g. [4]), but has also proved to be an effective tool to diagnose the nature of solute distribution in solidsolution crystals, whether metallic [8][9][10][11] or non-metallic, [12,13].…”