A new intermetallic phase in the W-Ni system

On the existence and the crystal structure of Ni4W, NiW and NiW2 compounds

“…Annealing time was chosen equivalent or larger than in previous studies at a temperature (950 C) around which NiW and NiW 2 were observed by other authors. Poulsen et al [7] observed the two phases between 800 C and 1010 C. Additionally none of the authors which have evidenced the phases at higher temperature notice decomposition a lower temperature. Bragg lines were observed by XRD.…”

“…In a composite material with thin W wires dispersed in a matrix of pure Ni and obtained by sintering, Poulsen et al [7] observed also by EPMA the presence of NiW together with a new phase of analyzed composition NiW 2 in the form of a thin (w5 mm) layer at the interface between the wires and the matrix. The two phases were observed in samples annealed in the temperature range 800-1010 C and the latter phase decomposed between 1010 C and 1040 C. A list of the positions of the diffraction lines relative to this new phase was given.…”

First principles, thermal stability and thermodynamic assessment of the binary Ni–W system

“…Poulsen et al [51] used W wires in pure Ni matrix and studied the samples with EPMA, and found NiW 2 , but the intensity data is missing in that work.…”

Interfacial reaction-controlled reprecipitation of W atoms in liquid matrix phase during the sintering of W-8 pct Mo-7 pct Ni-3 pct Fe

“…Various intermetallic phases also develop in these interdiffusion zones, in addition to the solid solution phases. [14,18,19] With further increase in sintering temperature, these intermetallic phases decompose into tungstenbased body-centered cubic phase and nickel-based facecentered cubic phase at peritectoid temperatures ranging from 970 ЊC to 1540 ЊC. The diffusion couples eventually decompose into solid and liquid phases at temperatures higher than the eutectic temperature.…”

“…[17] Thus, the competitive dissolution of tungsten and molybdenum in the liquid matrix phase, as suggested elsewhere, [7,[10][11][12] is found not to be a significantly important process. It may also be noted that the concentration of tungsten in the matrix phase for an isothermal holding time of 5 minutes was 54 wt pct, which is much higher than the maximum solubility of tungsten in nickel (30 wt pct), [14,18,19] that in Ni-30 wt pct Fe (16 wt pct), [14] that in Ni-15 wt pct Fe at 1480 ЊC (39.3 wt pct), [20] or even higher than the concentration of tungsten in the eutectic tungsten-nickel liquid phase (45 wt pct). Supersaturation of the matrix phase with tungsten in the early stage of isothermal hold was therefore the driving force for this system to reach the thermodynamic equilibrium state.…”