The effect of stacking fault energy on low temperature creep in pure metals

Abstract

Experimental results obtained by studying the low temperature creep behaviour before and after a small stress change are interpreted in terms of barriers due to intersecting dislocations. Using the data available on the temperature dependence of the flow stress in conjunction with these experimental results, estimates of jog energies are derived and compared with values obtained from flow stress data alone. Relative dislocation widths for various metals are also deduced. From the theoretical analysis relating dislocation width to stacking fault energy, tentative values are suggested for the stacking fault energies of Au, Ag, Al, Ni, Pb, Zn, Cd, Co and Pt, relative to that of Cu. These values are in reasonable agreement with previous estimates where available, thus confirming the hypothesis that low temperature creep is controlled by the proposed mechanism. The significance of these results is discussed in terms of the exhaustion and work hardening theories of low temperature creep. It is shown that the experimental observation that the apparent activation energy is insensitive to stress and pre-strain can be explained quito naturally on theories based on stress-aided activation and that it does not invalidate such theories.