Abstract
Reactive powder composites Cu-(0-15%)TiH2 containing up to 5% native Cu2O were manufactured by high energy ball milling and then hot-pressed to produce bulk nanostructured copper-matrix alloys reinforced by Cu3Ti3O inclusions. Two high-energy ball-milling (HEBM) protocols were employed for the fabrication of Cu-Ti alloys: single-stage and two-stage ball milling, resulting in an order of magnitude refinement of TiH2 particles in the reactive mixtures. Single-stage HEBM processing led to the partial retention of Ti in the microstructure of hot-pressed specimens as the α-Ti phase and formation of fine-grained (100-200 nm) copper matrix interspersed with 5-20 nm Cu3Ti3O precipitates, whereas the two-stage HEBM led to the complete conversion of TiH2 into the Cu3Ti3O phase during the hot pressing but produced a coarser copper matrix (1-2 μm) with 0.1-0.2 μm wide polycrystalline Cu3Ti3O layers on the boundaries of Cu grains. The alloy produced using single-stage HEBM was characterized by the highest strength (up to 950 MPa) and electrical conductivity (2.6 × 107 Sm/m) as well as the lowest specific wear rate (1.1 × 10-5 mm3/N/m). The tribological performance of the alloy was enhanced by the formation of Cu3Ti3O microfibers in the wear debris, which reduced the friction coefficient against the Al2O3 counter-body. The potential applications of the developed alloys are briefly discussed.