Sintering-free fabrication of high-strength titanium matrix composites reinforced with carbon nanotubes

To keep high structural integrity of carbon nanotubes (CNTs) in titanium (Ti), sintering and sintering-based consolidation processes were widely applied to fabricate CNTs/Ti composites. However, sintering processes were faced with the dilemma between insufficient densification at low sintering temperatures and excessive CNTs-Ti reaction at high temperatures. In this study, a sintering-free process combining cold compaction and hot extrusion (CC-HE) was developed to fabricate CNTs/Ti composites. The CC-HE-processed CNTs/Ti composites achieved superior tensile strength of 1262 MPa, which registered the new record among the pure Ti matrix composites reinforced with CNTs and graphene in available literature. By comparison study on CC-HE and the referential sintered CNTs/Ti composites, it was revealed that the high strength of CC-HE composites was attributed to the improved effects of grain refinement and secondary-phase strengthening, as a result of enhanced CNT integrity. The results provide a facile and large-scale-production pathway to fabricate high-performance carbon/Ti composites, which can be also applicable to other metal matrix composites.