Die experimentelle Bestimmung von Stapelfehlerenergien kubisch-flächenzentrierter Metalle

Abstract

The present paper gives experimental and theoretical results which enabel us to determine the absolute values of stacking-fault energies of face-centred cubic metals from the stress-strain-curves of single crystals. The activation energy for the crossslip of screw-dislocations is calculated as a function of the stacking-fault energyγ, the applied shear stressτ, and the size of the piled-up dislocation groups. An experimental value for the activation energy for cross-slip in copper is deduced from the strain-rate dependence of the shear stressτ _III at the beginning of stage III of the stress-strain-curve. Comparison between experiment and theory givesγ _Cu=170 ergs/cm².

The determination of the stacking-fault energy of other f.c.c. metals is possible by comparing the temperature dependence ofτ _III. Experimental results are given for Au and Cu. Data from the literature are used for Ag, Ni, and Al. We findγ _Au= 30 ergs/cm². The difference in stacking-fault energy of Cu and Au is much larger than was anticipated. It is substantiated, however, by a number of observations discussed in the paper. Constriction energies calculated on the basis of the newly determined stacking-fault energies are given.