A re-examination of the cottrell-stokes relation based on precision measurements of the activation volume

✍ Scribed by S. Saimoto; H. Sang

• Publisher: Elsevier Science
• Year: 1983
• Weight: 983 KB
• Volume: 31
• Category: Article
• ISSN: 0001-6160
• DOI: 10.1016/0001-6160(83)90133-5

✦ Synopsis

The predictionsofthe rateequation as applied to thermally activated plastic Row areexamined for thecase wheretheCottrell-Stokesrelation isstrictlyobeyed and arecompared to theexperimental results. For the temperature region below 0.25 T, where the pre-exponential is insensitive to stress and strain rate, it is immediately apparent that the stress is inversely related IO the strain ratesensitivity. In this temperature range preciseactivationvolumemeasurementson [OOl]aluminumcrystalsshow that theCottrell-Stokesrelation is observed at low stresses, but deviation from it is prominent at high stresses. This deviation is attributed to the plasticgeneration ofdefects which are more rate sensitive than monopole dislocations but contribute little to the flow stress. In the high stress region for both single crystals and polycrystalline material, the flow stress normaIized with respect tomodulusand temperaturecan becorrelated to theactivation volume and in turn to the familiar power law form with respect to strain rate. deuthch. Diese Aweichung wird der plastischen Erzeugung von Defekten zugeschrieben, die vie1 geschwindigkeitsempfindlicher als Einzelversetzungen sind, aber wenig zur FlieDspannung beitragen. Im Bereich hoher Spannungen kann die FlieBspannung von Ein-und Polykristallen-normalisiert bezfiglich Modul und Temperatur-mit dem Aktivierungsvolumen und daher mit dem bekannten potenzgesetz hinsichtlich der Dehngqschwindigkeit korreliert werden.