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

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 degrees C for 15 min. Electron microscopy and energy dispersive spectrometry analysis showed that annealing enhances the solid-state reaction. In the sample alter 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 alter accumulative HPT and post-deformation annealing is more uniform than alter 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 alter 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. Post-deformation annealing led to the formation of different quantity of intermetallic compounds in the studied samples.