Strain-rate cycling tests during Blaha-effect measurements were carried out in stages I, II and III of the stress-strain curve at 80 to 300K. On the basis of the plot of strain-rate sensitivity and stress decrement due to oscillation, the effect of strain upon the interaction between dislocations and impurities was investigated for Li+-doped (0.5mol% in the melt) and Na+-doped (0.5mol% in the melt) material. It had been reported that the curve appeared to reflect the effect of ultrasonic oscillations upon dislocation motion on a slip-plane containing many weak obstacles (such as impurities) and a few strong ones (such as forest dislocations). It therefore seemed that the Na+ ions in Na-doped material contributed to dislocation multiplication in the 3 stages, whereas the Li+ ions in Li-doped material did not contribute to it. The effective stress due to the impurities decreased with increasing strain, at almost all temperatures, in the case of Na-doped material. Thus, the critical temperature (at which the effective stress was zero) was larger in stage I, when compared with that in stage II, for Na-doped material; as deduced from the temperature-dependence of the effective stress.

Interaction between a Dislocation and Impurities in KCl doped with Li+ or Na+. Y.Kohzuki: Journal of Materials Science, 2000, 35[9], 2273-7