Mechanical, electrical properties and microstructures of combinatorial Ni-Mo-W alloy films

Abstract

Nickel-molybdenum-tungsten (Ni-Mo-W) alloys have been suggested for applications of advanced micro-electro-mechanical systems (MEMS) in extreme environments due to their high strength, good electrical conductivity, and excellent thermal stability. In this work, we have carried out combinatorial experiments to reveal composition-dependent phase formation, physical properties, and thermal stability of Ni-Mo-W alloy films. Combinatorial synthesis through a magnetron sputtering process fabricated thin films with a composition range of Ni56–92Mo6–38W0.5–7.5. Structural analysis for the as-deposited combinatorial film revealed that a nanotwinned and strongly textured nano-columnar fcc structure was formed in the Ni-rich compositions, while solute content greater than 30% resulted in the formation of metallic glasses. The specimen exhibited very high hardness (8.8–12.5 GPa) and moderate electrical resistivity (85–135 μΩ ∙ cm), and both the properties were found to increase with solute concentration. Annealing of the combinatorial film at 600 ℃ for 1 h revealed that nanotwinned structure is thermally stable for high Ni concentrations. Metallic glasses with high solute concentration also exhibited high thermal stability and were not crystallized after annealing. Alloys with intermediate solute content experienced the transformation from the amorphous to fcc nanocrystalline phase with nanotwins. The annealed combinatorial film maintained high hardness and moderate electrical resistivity after annealing.