Some aspects of serrated yielding in substitutional solid solutions of iron

摘要: Abstract Serrated yielding was observed between 500 and 775°K in alloys of iron which exhibited marked solid-solution hardening. The serrations result from the formation bands localized deformation. In a soft machine where applied load remains constant, band spreads immediately over entire gauge length. hard burst strain associated with causes to drop, so that spreading front stops when stress falls below critical level. During reloading, aging dislocations occurs. At low temperatures little occurs during propagates along length only small undulations load. higher temperatures, is more rapid, becomes pinned reloading can move by breaking away. Alternate breakaway recurs as length, producing regular on load-extension curve, surface markings specimen. serration height Δθ increases increase time, t, temperature, T, according = A + BlogZ, B are constants Z t exp ( −Q RT ) . apparent activation energy for appearance growth serrations, Q, about half diffusion substitutional atom iron. negative results vacancy annealing experiments, failure criterion indicate high diffusivity not due deformation-induced vacancies. Rather, suggest pinning redistribution or reorientation solutes solute clusters dislocation cores. upper dependent rate, growing abruptly disappear. rate appears be just allows one lattice jump serrations. disappearance near