Microstructure and Mechanical Property of α-Al–Zn–Cu Alloys Aged at Room Temperature

Abstract

Al–Zn–Cu alloys with five different compositions in the α-phase region have been prepared and their microstructures have been characterised employing X-ray diffraction, optical and scanning electron microscopy. The mechanical property of the alloys has also been characterized from the measure of hardness. A close correlation between the microstructure and hardness of the alloys has been observed. X-ray studies of ageing at room temperature of the materials in the deformed state revealed faster stress-induced precipitation of Zn and Cu whereas the transformation is slow in the homogenized materials. The rate of G.P. zone formation is either very slow or not detectable. The results of phase-transformation study have been supplemented by DSC study along with subsequent measurement of hardness values which are reduced on completion of Zn and Cu-rich precipitations.