Strengthening of Al-Cu single crystals by stress-oriented Guinier-Preston zones

Abstract The strengthening of Al-Cu is examined after introducing Guinier-Preston (GP) zones on particular cube planes by stress ageing. A compressive stress applied during an early stage of ageing promotes formation of the platelet precipitates on the cube planes subjected to the largest normal stress. Selection of a stress axis in the compression tests after the stress ageing enables one to change the slip system geometry with respect to these platelet obstacles. It is shown that the GP zones cut by moving dislocations contribute to the strengthening at low temperatures, accompanying strong orientation dependence. The origin of the strengthening is discussed on the basis of the thermal and athermal nature of the dislocation interaction with the stress-oriented planar GP zones.