カドミウム単結晶の{11\bar22}⟨\bar1\bar123⟩ 2次錐面すべりによる降伏応力の異常温度依存性の支配機構

Abstract

The mechanism of anomalous temperature dependence of yield stress by {11\bar22}〈\bar1\bar123〉 second order pyramidal slip in Cd single crystals in proposed. (c+a) edge dislocations are immobilized as a result of thermally activated dissociation, i.e., (c+a)→>(c sessile dislocation)+(a basal dislocation). Increase in frequency of the immobilization with increasing temperature decreases the mean moving distance of (c+a) edge dislocations and consequently the amount of strain in slip bands. In order to maintain the constant strain rate at higher temperature, the velocity of slip band propagation by double cross slip of (c+a) screw dislocation to the next near slip plane must be increased by higher stress. Therefore, the yield stress increases with increasing temperature. The mean moving distance of (c+a) edge dislocation is nearly constant when the strain rate is increased. Then, the higher stress for increasing the slip band propagation velocity is needed to compensate for the increased strain rate. The yield stress, therefore, increases with increasing strain rate.The negative temperature dependence of the yield stress below 133 K is considered to be caused by the deformation controlled by the Peierls mechanism.