Microstructural evolution and mechanical properties of carbon nanotubes–reinforced TZM composites synthesized by powder metallurgy

A strategy utilizing carbon nanotubes (CNTs) was put forward to prepare Titanium–zirconium–molybdenum (TZM) composites, which comprised Mo–0.5Ti–0.1Zr–0.03CNTs (wt.%), via high–energy ball milling (HEBM), followed by spark plasma sintering (SPS). The microstructural evolution of the TZM composite powders and the sintered samples were characterized by X–ray diffraction (XRD) and scanning electron microscopy (SEM). Their Vickers hardness and compression mechanical properties were also investigated. Results revealed that during the HEBM of TZM composite powders, the fracture mechanism dominated the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. An increase in milling time resulted in decreased grain size and increased lattice parameter. The changes in microstructure of the composite powders induced by ball milling improved the relative density, Vickers hardness, and yield strength. Transmission electron microscopy (TEM) showed that during long ball–milling time, a Mo–Ti–Zr solid solution formed with the addition of Ti and Zr after sintering. Second–phase particles (TiZrC2) and many dislocation lines were found in the deformed samples.