Metallic glasses lack defects like dislocations in crystals. On one hand, the absence of defects bestows high strength. On the other hand, the consequent ductility and fracture toughness become the main limiting factors for wide application. Hence, this work focuses on investigating the mechanical response of an electrodeposited NiP metallic glass, in particular, at different strain rates and sub-ambient temperatures, which helps understand the deformation and failure mechanism. Since NiP is frequently applied as films, either for hard coating or as diffusion barrier between Cu and Si in semiconductor industries, in situ micromechanical tests are performed on micro samples fabricated by focused ion beam. The testing strain rates can cover seven orders of magnitude (10^-3 s^-1 to 1000 s^-1) and the testing temperature can be 100 oC lower compared to the commonly applied RT. 

Upon changing temperatures, the yield strength is well predicted by the cooperative shear model, implying that the plasticity in NiP is dominated by the activation of shear transformation zones. The as-deposited NiP exhibits a two-stage strain rate sensitivity, specifically nearly insensitive at the lower strain rate range to a clear positive sensitivity at the higher range. This transition, as reported elsewhere, correlates with the diffusion-assisted atomic relaxation and percolation of nucleated shear transformation zones. Besides, an increased multiplication of shear bands is observed either with increasing strain rate or with decreasing the testing temperature. Since failure in metallic glasses mainly originates from the induced softening by localization of shear bands, an increase in shear band density is supposed to correlate with an improved ductility, which motivates us further for following microscale fracture tests.