Thin flat single crystals of Cu—5 to 15 at% Al oriented for single glide are uniaxially elongated with a constant rate of at room temperature. The evolution and propagation of a small active zone of localized shear, the “Luders band front” (LBF), is observed by both light and electron microscopy during and after deformation, respectively. Finite element computer simulations are applied to investigate the influence of the characteristic shape of the specimen in the LBF on the local shear stress distribution in parallel slip planes. The results as well as the observed lattice rotation across the LBF suggest the introduction of excess dislocation arrangements. Their self-shear stress fields, calculated under the assumption of linear elasticity, reveal local stress concentrations in the vicinity of the slip steps in the LBF which give an explanation for the observed slip structure over three orders of magnitude. The dependence on crystal geometry and solute concentration as well as the propagation kinetics of the Luders band are discussed.
Dunne, flache, mittelorientierte Cu—5 bis 15 At% Al-Einkristalle werden bei Raumtemperatur im einachsigen Zugversuch mit einer konstanten Rate von verformt. Die Entwicklung und Ausbreitung einer schmalen aktiven Zone lokalisierter Scherung, der “Ludersbandfront” (LBF), werden jeweils sowohl im Licht- als auch im Elektronenmikroskop wahrend bzw. nach der Verformung beobachtet. Mit Hilfe der Methode der Finiten Elemente wird in Computersimulationen der Einflus der charakteristischen Probenform in der LBF auf die lokale Scherspannungsverteilung in parallelen Gleitebenen untersucht. Die Ergebnisse legen zusammen mit der beobachteten Kristallgitterrotation entlang der LBF die Einfuhrung von Uberschusversetzungsanordnungen nahe. Deren Eigenscherspannungsfelder, die unter der Annahme der linearen Elastizitatstheorie berechnet werden, weisen in der Nahe der Gleitstufen der LBF lokale Spannungskonzentrationen auf, mit denen sich die beobachteten Gleitstrukturen uber drei Grosenordnungen erklaren lassen. Der Einflus der Probengeometrie und der Legierungskonzentration sowie die Ausbreitungskinetik eines Ludersbandes werden diskutiert.
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