Effect of annealing on the structure and phase composition of Cu-Al composite produced by conventional and accumulative HPT

Abstract

The paper presents the first results of the investigation of the effect of annealing on the evolution of microstructure and phase composition of a Cu-Al composite obtained by accumulative high pressure torsion (HPT). Cu-Al composites produced under 6 GPa in 10 revolutions at room temperature with conventional and accumulative HPT were annealed at 450°C for 15 min. Electron microscopy and energy dispersive spectrometry analysis showed that annealing enhances the solid-state reaction. In the sample after conventional HPT and post-deformation annealing, grayer contrast layers containing intermetallic compounds were formed at the copper-aluminum interface. The contrast on the microstructure images of the sample after accumulative HPT and post-deformation annealing is more uniform than after conventional HPT and annealing. In the sample, a more intense phase transformation occurred. This led to a noticeable increase in the volume fraction of the intermetallic compounds up to 5 -6 times. X-ray diffraction analysis indicates that in the annealed sample after accumulative HPT, alongside with initial copper, there is also a solid solution of aluminum in copper, which differs from copper with a crystal lattice parameter. Postdeformation annealing led to the formation of different quantity of intermetallic compounds in the studied samples.