A Hot Extrusion Process without Sintering by Applying MWCNTs/Al6061 Composites

For carbon nanotube (CNT)/Al composites, compaction forming is conducted for densification processing, and then sintering and secondary processes are conducted. This general process has problems such as the complexity of the processing procedures, and high manufacturing costs. This study presents a hot extrusion process without sintering for fabrication of CNTs/Al6061 composites. Before hot extrusion, preforms are fabricated by the compaction process for the mixture of Al6061 power and CNTs. Several hot extrusion experiments were performed under six types of CNT content; three extrusion ratios and three extrusion temperatures. The formability increased as the extrusion temperature increased for low CNT content. At 620 °C, the forming of all materials except for 10 vol % CNTs/Al6061 was possible at extrusion ratios R = 4, R = 8, and R = 16. As CNT content increases, extrusion pressure almost linearly increases. As the extrusion ratio increases, the extrusion pressure increases. The amount of CNT content increases as Vickers hardness increases. The Vicker’s hardness of 1 vol % CNTs/Al6061 billet is about 100 HV while that of 10 vol % CNTs/Al6061 billet is about 230 HV. There are no significant differences of compression stress according to extrusion ratio as observed in terms of pure Al6061, 1 vol % CNT/Al6061, and 3 vol % CNTs/Al6061.