Abstract

A new first-order physical theory of long-term strength based on a dislocation model and analytical rateequations has been advanced for describing dynamic (time-dependent) microyield/creep resistance responsible for a potentially useful measure of the uniform strain preventing a premature fracturing of rapid-hardening crystals. Such a diagnostic approach enables the short-range rate-controlling mechanisms to be identified for stressed crystals in terms of the thermoactivation (numerical) analysis of rapid strengthening using the constant structure steady-state creep tests and dislocation relaxation technique. For the alloys under consideration, a more accurate (dislocation) criterion of useful long-term strength is formulated for solution-hardened alloys in which the threshold dragging stress as a function of uniform strain resistance is directly related to the elastic (shear) stability of a dislocated crystalline lattice, velocity, and density of sliding dislocations as well as their line tension in the stress field. The criterion could be used for the quantitative assessment of the short-range dragging effects preventing a transition from the structurally uniform sliding to the localized shear strain that governs a premature fracture of metal crystals.

Keywords: Strength; Diagnostic approach; Dislocation resistance

Abbreviations: DSA: Dynamic Strain Aging; PLC: Portevin-Le Chatelier; AE: Energy of Activation; AV: Activation Volume