Basic Physics of Long-Term Strength of Solid Solutions with Various Kinetics of Mobile Defects

Abstract

A new dynamical model of time-dependent dislocation microyielding has been proposed using the propounded structure-energy-concept of long-continued strength in terms of dragging mechanisms responsible for microyield resistance increase in solid solutions below macroscopic yield stress. A physical theory of long-term, non-destructive strength is being developed taking as a basis the derived relations for strain rates in metal alloy systems with mobile modes of dislocation pinning. The new approach, thermoactivated analysis and energy (dislocation, quantitative) criterion of time-dependent strength account for influence of the short-range dislocation-solute interaction in real scale of time and predicts a transition from homogeneous to localized shear deformation contributing to a probable fracture. In accordance with the revised equations of the dislocation stress relaxation and derived energy relations the threshold stress of long-term strength of a given alloy is associated with shear instability of its dislocated crystalline lattice, density and rate of sliding dislocations, their excess energy (line tension) as well as fields of internal elastic stresses produced by solutes. The theoretical results are in reasonable agreement with published experimental data obtained by using dislocation relaxation and creep strain rate measuring techniques. They are suitable to advanced alloys with the Portevine–Le Chatelier effect, and could be useful for quantitative assessment of alloying effectiveness, potential of heat-resistance and expected service resource.

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