Synthesizing and characterization of Cu-WC-Si composite prepared by using planetary ball milling
Cu-WC-Si composites were synthesized by using a planetary ball milling. Different composition of elemental Cu, WC and Ti powders were mixed and milled for 5 and 10 hours in an open air. The powder characterized before and after milling to expose the effect of milling variables on particle size, homogenization and contamination. Analyzing carried out by using X-ray and scanning electron microscope (SEM). The as milled particle size and homogenization generally influenced by milling time and tungsten Carbide (WC) content. With longer milling time and higher tungsten carbide content, particle size becomes smaller and smaller. The average particle sizes of the as milled powder are in ranged from 5µm to 30 µm and strongly depend on the copper content.
Synthesis of nanocrystalline copper–tungsten alloys by mechanical alloying
Abstract Copper–tungsten exhibits total absence of solubility in both solid and liquid state. Mechanical alloying (MA) as a solid state, non-equilibrium process can be beneficial to the processing of such an immiscible system with the added features of refinement of structure. A study was undertaken to synthesise various Cu–W alloys and develop an ultrafine microcomposite structure of tungsten in copper matrix by mechanical alloying. Elemental powders of copper and tungsten were milled in high energy ball mills. The milling behaviour was found to depend on the composition, milling time and milling atmosphere. The milled powders were characterised for their particle size, microstructure and lattice parameters. Metastable mutual solid solubility in the system was confirmed. Crystallite sizes were found to be in the nanocrystalline regime. The conversion of milling energy effectively to generate deformed surfaces, which in turn led to metastable solid solubility and nanocrystalline structure, was aided by the presence of oxygen in the milling atmosphere.
Influence of dynamic densification on nanostructure formation in Ti5Si3 intermetallic alloy and its bulk properties
Abstract Dynamic densification was used to consolidate mechanically amorphized Ti–Si alloy powders, using a three-capsule, plate–impact, gas–gun loading system at velocities of 300, 500, and 700 m s −1 . The dense compacts were subsequently crystallized at annealing temperatures in the range of 800–1200°C, for time periods of 1–12 h. The compacts were observed to crystallize to a typically single-phase Ti 5 Si 3 compound and an ultra-fine grain microstructure, based on TEM and XRD analysis. The average grain size changed from ∼50 nm upon heat treatment at 800°C for 1 h, to ∼160 nm at 1200°C for 3 h, however, it remained stable (∼115–125 nm) during annealing at a constant temperature of 1000°C and increasing heat treatment time from 1 to 12 h. In-situ crystallization studies performed by heating the dynamically-densified samples in the TEM at temperatures up to 900°C, revealed that the increase in fraction of amorphous to crystalline phase was occurring by an increase in the number density of nucleating crystallites, and not via significant growth of existing crystallites since their growth is inhibited by the impingement of the crystals. Vickers microhardness measurements showed values of 1200–1400 kg mm −2 for grain size ranging from ∼60 to 160 nm. While these microhardness values are ∼80% higher than those for microcrystalline shock-densified Ti 5 Si 3 alloy, the fracture toughness values measured using the indentation method were observed to be ∼2–4 MPa√m, which is typical of that of brittle ceramics.