Effectively reinforced load transfer and fracture elongation by forming Al4C3 for in-situ synthesizing carbon nanotube reinforced Al matrix composites

This work presents an in-situ chemical vapor deposition (CVD) method to synthesis carbon nanotube (CNT) on Al powders in a vertical tube furnace. The carbon nanotube reinforced Al matrix composites (CNT/Al composites) were fabricated by a new powder metallurgy (PM) approach associated with vacuum induction melting technique. It was shown that CNT was homogenously distributed in the Al matrix, and an interfacial transiting layer of Al4C3 was formed between Al matrix and CNT in the bulk material. The tensile test showed that 1.5 vol% CNT/Al composites exhibited the largest tensile strength of 191 MPa as well as an excellent elongation of 32.6%. The strengthening efficiency of the 1.5 vol% CNT/Al composites improved by ~ 80% compared to the unreinforced pure Al. The strengthening mechanisms were mainly attributed to the load transfer of CNT, Al4C3 and dislocation strengthening. The Al4C3 transiting layer was beneficial to increase the interfacial shear strength and prolong the slide deformation of dislocation by forming an orientation relationship of Al4C3 <001> // Al <111> and CNT (002) // Al4C3 (001) according to the transmission electron microscope (TEM) observation. Besides, the thermocycling measurement enriched and deepened the understanding of the effect of Al4C3 on improving the interfacial bonding, degrading the interfacial thermal mismatch between CNT and the Al matrix and increasing the compactness of the CNT/Al composites.