Thermal Stability and Mechanical Properties of Nanotwinned Ni–W Alloyed Films

Nanocrystalline alloys often exhibit unusual thermal stability as a consequence of kinetic and thermodynamic barriers to grain growth. However, the physical mechanisms governing alloy stability need to be identified. In this work, we found that grain boundary (GB) relaxation renders Ni–W alloyed films relatively stable at low annealing temperature, while twinning-mediated grain growth occurs via dislocation-GB/twin boundary (TB) interactions as the annealing temperature increases. At a relatively low temperature, TB strengthening plays a dominant role in plastic deformation, whereas precipitation strengthening gradually controls the deformation mechanism with the increase of annealing temperature. Our findings provide evidence for improving mechanical property through alloying and microstructure design, and have a crucial guiding significance in material selection and miniaturized applications such as Micro Electro Mechanical Systems.