Microstructural and mechanical investigations of powder reinforced interface layer of hot extruded Al/Cu bimetallic composite rods

In this study, the Aluminum/Copper (Al/Cu) bimetallic composite rods were fabricated using a new method consisting of the hot extrusion process with different extrusion temperatures, volume fractions of participating metals, and types of reinforcement powders in the interface layer. Microstructural and mechanical properties of extruded bimetal composite rods and their interface layers were entirely investigated using optical microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), and also compression, shear strength, and microhardness tests. Three types of Al/Cu composites with volume percentages of 30, 42, and 51% Al were fabricated at two extrusion temperatures of 400 degrees C (IET4) and 500 degrees C (IET5). In the next step, the interface layers were reinforced with four types of Cu, Al, a combination of Al and Cu (Al-Cu), and Al2O3 powders. The OM metallography results showed that the copper sleeve has a more twining and elongated grain perpendicular to the extrusion direction (ED), which indicates dynamic recovery (DRV) is the dominant mechanism at 400 degrees C. In contrast, hot extruded samples at 500 degrees C showed fine recrystallized grains forming around the prior grain boundaries. It was found that volume fractions significantly affect the flow behavior of composite samples as the extrusion force decreases with increasing the volume fraction of Al. During compression tests at the high value of strain, fracture occurred in the interface layer of composite samples with volume percents of 42 and 51% Al. However, there is good bonding and diffusion at the interface layer reinforced, especially with Cu and Al-Cu as reinforcement powders. Also, EDS analysis showed that the CuAl3 intermetallic phase appeared at the interface layer of the Al/Cu composite.