Effect of compositional undulation on the mechanical behavior of atomic-scale planar-faulted Ni-Mo-W films

Ni exhibits exceptional resistance to heat and corrosion, making it a sought-after material for harsh environment applications. The introduction of low interfacial energy planar defects (e.g., nanotwins and stacking faults) can greatly enhance the mechanical properties of Ni at elevated temperatures, but this strategy generally remains difficult due to Ni's high stacking fault energy (120-130 mJ/m(2)). Here, we apply HRSTEM, APT characterization, and DFT calculation to discover that inhomogeneous distribution of Mo atoms can facilitate the nucleation and stabilization of atomic-scale stacking faults in Ni-Mo-W thin films, in addition to the increase in global concentration. Micro-tensile experiments confirm the exceptionally high tensile strength up to 3 GPa. Post-mortem TEM analysis reveals that de-faulting followed by selective activation of dislocation emission and glide are the strength-limiting deformation mechanism. This work provides a practical strategy for designing ultrahigh strength, stable nanostructured materials by local chemical undulation.