Philosophical magazine. A/Philosophical magazine. A. Physics of condensed matter. Structure, defects and mechanical properties · 1999 · 13 citations · 6 references
Natural SciencesMaterials EngineeringMaterials ScienceCrystal StructureMechanical Behavior Of MaterialsSolid State PhysicsDeformation MechanismsDislocation MechanicsDislocation TheoryPlastic DeformationDislocation BehaviorDislocation ClimbDislocationsEdge DislocationsGlide PlanesPartial DislocationsShockley Partial DislocationsYield Stress
Abstract A yield stress anomaly has been observed for ½[112](111) slip in single crystals of γ-Ti-54.5 at.% Al. Weak-beam electron microscopy studies have been carried out to elucidate the origin of this anomaly. At room temperature, screw and 60° dislocations are dissociated in the glide plane, and 30° dislocations are dissociated by glide on intersecting {111} planes, forming weak locks. At high temperatures, ½[112] dislocation loops are elongated along their edge direction, and these edge dislocations are dissociated by climb and glide into sessile configurations consisting of Frank and Shockley partials on different intersecting {111} planes, with a stair-rod dislocation along the line of intersection. There is some evidence for further dissociation of the Frank partial. These strong locks are responsible for the yield stress anomaly. The driving force for the anomaly is the reduction in dislocation energy; the mechanism involves climb, which becomes easier with increasing temperature.
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