Microstructure and properties of carbon nanotubes-reinforced magnesium matrix composites fabricated via novel in situ synthesis process

Abstract A novel carbon nanotubes (CNTs)-reinforced magnesium (Mg) matrix composite was successfully fabricated via an in situ synthesis of Mg on the surfaces of CNTs and a powder metallurgy (PM) process. The nanoscale Mg grains were first synthesized in situ on CNTs via the solid-state displacement reaction of lithium (Li) to Mg in anhydrous magnesium chloride (MgCl2) to obtain Mg-encapsulated CNTs (CNTs@Mg) composite powders. These were used to fabricate CNTs@Mg bulk composites via the PM method. In the CNTs@Mg in situ composite structure, the synthesized Mg grains were in contact with CNTs in a stacking manner, and nanoscale contact and diffusion bonding occurred at the CNTs–Mg interface, realizing not only strong interface bonding between CNTs and Mg but also the dispersion of CNTs in the Mg matrix. The CNTs@Mg composites exhibited improved mechanical properties. The microhardness, ultimate tensile strength (UTS), and breaking elongation of 4.0 wt% CNTs@Mg bulk composite were increased by approximately 43.5%, 33.4%, and 31.3% compared with pure Mg bulk, respectively. Furthermore, the mechanical properties of the CNTs@Mg bulk composites were superior to those of CNT/Mg composites fabricated via the traditional addition process. Therefore, the investigated CNTs@Mg composites are promising candidates for the field of lightweight structural materials.