Investigation of microstructure and strengthening mechanism in CNTs reinforced Mo-based composites

The carbon nanotubes (CNTs) reinforced Mo-based composites were fabricated by an efficient powder metallurgy method, including acid treatment, wet dispersion, ball milling (BM) and spark plasma sintering (SPS). The sintered Mo-based composites possess high relative density (99.1%) and compressive yield strength (970 ± 10 MPa). Acid treatment and wet dispersion effectively address the problems of the agglomeration and subsequent uniform distribution of the CNTs in the composite powders. After BM and SPS, ultrafine-grained composites with a grain size of 1.84 μm and a nanoparticle size of less than 200 nm were obtained. A mechanism for purification and strengthening is proposed. On the one hand, Hf and HfC can adsorb nearby oxygen impurities and purify the Mo matrix. On the other hand, the incoherent interface between Mo and nanoparticles acts as primary dislocation nucleation and prevents the propagation of secondary dislocations, which in turn leads to strain hardening.