Development of a modified shearing cooling roll process for carbon nanotube reinforced aluminum composites

Semi-solid metal processing offers a potential route for incorporating carbon nanotubes (CNTs) into aluminium alloys while mitigating the flotation and thermal degradation commonly encountered during liquid-state processing. In the present work, a Shearing Cooling Roll (SCR) process, previously developed for processing alloys, was adapted for the first time for composite fabrication through the integration of an argon-shielded powder injection system that delivers MWCNTs directly into high shear semi-solid A356 slurry at 580–600 °C. The processing conditions were designed to promote reinforcement incorporation while limiting CNT degradation. A356-MWCNT composites containing 0.1, 0.3, and 0.5 wt% MWCNTs were produced using the SCR process to establish the influence of the proposed processing route on reinforcement incorporation, microstructural integrity, and mechanical performance. XRD and Raman spectroscopy provided evidence for successful CNT incorporation while indicating preservation of CNT structural integrity and limited interfacial reactions, with the I D /I G ratio increasing from 0.74 to 0.99 and Al 4 C 3 formation only at 0.5 wt%. The 0.3 wt% composite exhibited the optimum performance after T6 treatment, achieving a yield strength of 306 MPa, ultimate tensile strength of 385 MPa, and hardness of 123 HV5, corresponding to a 20% increase in UTS over the T6-treated base alloy, and 60% improvement relative to the as-cast base alloy. Fractography and HRTEM observations further confirmed effective CNT-matrix interaction following SCR processing. These results demonstrate the potential of SCR as a semi-solid processing route for incorporating CNT reinforcement into aluminium alloys while addressing the reinforcement incorporation challenges associated with conventional casting.