Accession Number:

AD0613726

Title:

THE DEPENDENCE OF CROSS-SLIP ON STACKINGFAULT ENERGY IN FACE-CENTRED CUBIC METALS AND ALLOYS,

Descriptive Note:

Corporate Author:

CAMBRIDGE UNIV (ENGLAND) CAVENDISH LAB

Report Date:

1962-06-05

Pagination or Media Count:

21.0

Abstract:

The results of an experimental study of the temperature and strain-rate dependence of tau sub III the stress at the onset of stage III for Cu-Zn alloys are described and interpreted in terms of Seegers theoretical analysis of tau sub III the stress at the onset of stage III. The values of the stacking-fault energy, gamma, derived in this way are compared with the estimates of gamma for the same alloys obtained directly from electron microscope observations of dislocation nodes. The two sets of values are found to disagree, and the nature of the discrepancy is such as to throw serious doubts on the applicability of the Seeger analysis to Cu-based alloys with ea1.10. The lower limits of gamma for pure Cu and Ag, from electron microscope data, are approximately 60 ergssq cm and approximately 20 ergssq cm the values of gamma deduced from Seegers tau sub III analysis are approximately 170 ergssq cm and approximately 30 ergssq cm respectively. The lower limit of gamma for Cu is inconsistent with the previously accepted figure based on the assumption that gamma is twice the twin boundary energy, and this assumption is now held to be invalid. Seegers model of cross-slip at Lomer-Cottrell barriers is examined critically, and found to be incompatible with the observations in Cu and Al that screws are held up preferentially. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE