Fabrication of VGCF reinforced aluminum matrix composites by powder can extrusion and investigation of their reinforcing mechanism

Aluminum matrix composites reinforced by vapor grown carbon fibers (VGCF) were fabricated by powder can extrusion. Extrusion ratio was 9 or 16. Temperature and heating duration were changed to investigate the effect of extrusion condition on properties of composites. Measurement of micro-Vickers hardness, tensile strength was conducted and micro structure such as VGCF orientation was characterized. When extrusion temperature was higher or when heating duration was longer, mechanical strength was lower, but fracture strain was higher. In addition, reinforcing efficiency to aluminum was higher for longer heating duration and higher extrusion ratio, due to improved VGCF orientation. Strength was modeled considering load bearing by VGCF, VGCF orientation, work hardening of matrix due to thermal expansion mismatch of VGCF and aluminum and Orowan looping mechanism. From those results and the observation of aluminum grain in composites, reinforcing mechanism of VGCF reinforced composites was discussed.