Effect of prestrain on the strength anomaly in β-brass

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Abstract
The effect of prestraining at room temperature on the occurrence of the strength peak at around 200°C in 8-brass has been studied using single crystals with orientations close to the boundary connecting [111] and [011] of the standard triangle. It has been shown that the mode of deformation in which the crystals are prestrained at room temperature has a profound effect on Tp (the temperature at which the yield stress shows the peak in the yield stress versus temperature curves) obtained in the subsequent deformation at high temperatures. When crystals are prestrained in compression, the Tp value obtained in the second deformation is close to the T, value obtained on virgin crystals in compression whereas, when crystals are prestrained in tension, the Tp value obtained in the second deformation is close to the Tp value obtained on virgin crystals in tension. It was also confirmed by transmission electron microscopy observation of dislocations and also analyses of axis reorientation during deformation that the transition of the slip direction from 〈111〉 below Tp to non-〈111〉 above Tp takes place irrespective of whether the crystals are prestrained or not.