The thermal stability of Ni–Mo and Ni–W thin films: Solute segregation and planar faults

Anomalously high density and thermal stability of nanotwins in Ni(W) thin films: Quantitative analysis by x-ray diffraction

“…This prediction cannot be supported by experimental evidence, since in practice films with such high W contents were found to be amorphous after deposition. 12 The latter experimental result might be suggested recognizing the observed slight decrease of the quotient 'degree of hexagonality to W content' at high W concentrations.…”

“…The planar-fault density, which is defined with respect to face-centered cubic (fcc) stacking in the present work, depends on the W content: At low W content the Ni(W) films are a fcc-like solid solution, with Ni being replaced substitutionally by W, whereas for W contents .20 at.% the crystal structure of the solid solution cannot be described as fcc anymore; instead, the crystal structure of the solid solution can be conceived as (mainly) faulted hexagonal close-packed (hcp). 12,16 This, on first sight puzzling observation, could be successfully explained very recently on the basis of first-principles calculations which suggested that a hcp solid-solution phase is more stable than a fcc solid-solution phase in the considered concentration range. 16 The present work aims at (i) quantitative analysis of the planar-fault density for Ni(W) films of different W contents and (ii) investigation of the thermal stability of the planar faults.…”

“…The presence of a high density of nanotwins was revealed. 11,12 The nanotwinned microstructures of these Ni(W) solid-solution films resemble to some extent those of pure nanotwinned metals such as Cu. The nanotwinned Cu microstructures were shown to be responsible for distinctly enhanced hardness, tensile strength, and resistance against fatigue, even in combination with ductility larger than for their nanocrystalline, untwinned counterparts.…”

“…3,4 Nanocrystalline Ni-W films were produced successfully by electrodeposition and were found to exhibit outstanding mechanical properties and corrosion resistance. [5][6][7][8] In recent years, magnetron-sputtered Ni-W films were investigated, [9][10][11][12] focusing on the microstructure of these films. The presence of a high density of nanotwins was revealed.…”

“…11,12 The grains exhibit a high density of planar faults, aligned perpendicular to the film-growth direction. The planar-fault density, which is defined with respect to face-centered cubic (fcc) stacking in the present work, depends on the W content: At low W content the Ni(W) films are a fcc-like solid solution, with Ni being replaced substitutionally by W, whereas for W contents .20 at.% the crystal structure of the solid solution cannot be described as fcc anymore; instead, the crystal structure of the solid solution can be conceived as (mainly) faulted hexagonal close-packed (hcp).…”