Papers by Keyword: Dynamic Dislocation Interaction

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Authors: Shigeo Saimoto, S. Subbaiyan, C. Gabryel
Abstract: In dynamic dislocation-defect analysis, the thermodynamic deformation-mode signatures are examined as the ageing proceeds. In this method, the activation volume (ν) and the mean slip distance (λ) is simultaneously determined with the flow stress (τ) such that the inverse workhardening slope (1/θ) can be plotted versus b2λ/ν where b is the Burgers vector. The slope of this almost linear locus is directly proportional to the activation distance (d). Calibration with a model alumina-dispersed high conductivity copper reveals that punched-out loops are produced up to failure and is represented by a linear locus from 0.1 to 11 % strain. Artificial ageing of AA6111 at 180°C follows this pattern but the naturally-aged specimen manifest a distinctly different signature which shows a transition as the GP zone-type precipitates are sheared. Furthermore by selecting a suitable tensile-test temperature below 250K, the particle size and volume fraction can be determined if particle shearing does not take place. The optimum size and volume fraction necessary for sufficient strength and ductility can be assessed using this method.
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Authors: Shigeo Saimoto
Abstract: Measurements of the activation volume and mean slip distance were used in the dynamic dislocation-defect analysis to reveal the dislocation-obstacle evolution with strain. Due to the large effect of point defect mobility above 250 K on the strain rate sensitivity, fine-grained Al specimens with the grain-boundaries sealed and unsealed as vacancy sinks were tested at 300 K as the reference behaviour. The activation distance diagrams revealed that the artificially aged products in AA6111 and naturally aged extruded AA6063 can be used to examine the effect of chopping-up of particles on the ductility of the samples. Thus a means to examine strength-structure-ductility of specific products have been devised.
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