A strategy to examine microstructure dependent fatigue behavior of tungsten fine wires

To meet the ever-growing demand for specialized products, new alloys and a deeper understanding of fundamental material properties and failure mechanisms are required. Here tungsten is of particular interest due to its exceptional mechanical and physical properties, including high elastic modulus, tensile strength, thermal stability, and wear resistance. However, for long-term dynamic applications, the influence of microstructure on material fatigue properties becomes crucial. A relevant product being used increasingly frequent at room temperature are tungsten fine wires. Due to the small wire diameter of less than 150 μm, micro- and nanomechanical tests have to be utilized to explore the fatigue behavior of such tungsten fine wires. Therefore, a novel small-scale fatigue setup was realized, whereby, a micron sized cantilever is milled into the clamped wire using a focused ion beam microscope. This cantilever was then tested with an open-load feedback controlled in situ nanoindenter inside a scanning electron microscope at room temperature. Thereby, the threshold of the stress intensity factor range could be quantified as 3.7MPam[jls-end-space/], and favorably compared to existing bulk data of single crystalline tungsten.