Synthesis and mechanical properties of co-deposited W nanoparticle and ZrCuAg metallic glass thin film composites

The combination of conventional physical vapor deposition and a gas aggregation nanoparticle source enabled the study of model systems of unique material combinations and dimensions. Zr50Cu45Ag5 thin film metallic glasses with varying contents of single-crystalline 5 nm tungsten nanoparticles were synthesized using this technique. This approach provides precise control over nanoparticle shape, size, distribution, and concentration. The films were later annealed at 150 degrees C, 250 degrees C, 350 degrees C, and 450 degrees C. At room temperature inclusion of 0.01 vol% tungsten nanoparticles caused a 15% increase in the nano-indentation hardness of a thin film metallic glass, while having no significant effect on pop-in length or frequency, as seen in the loading curves. Even more remarkably, at 450 degrees C a control film containing no nanoparticles experienced significant segregation and subsequent crystallization, whereas this effect was repressed in the tungsten nanoparticle composite thin film metallic glass. Unobstructed by nanoparticles, at high temperatures zirconium diffused to the surface of the film, forming a crystalline layer of up to 80 nm. In contrast, this layer is kept to below 30 nm when the nanoparticles are present. The stabilization of the microstructure is also clear from indentation results, while the hardness of the reference sample changes significantly due to the undesired crystallization, the hardness of the composite remains constant.