Strain-rate sensitivity of strength in macro-to-micro-to-nano crystalline nickel

► Grain refinement enhances the strength of nickel from the micro-to-nano scale. ► The strain-rate sensitivity of strength is measured using tensile and micro-scratch testing. ► Nano-crystalline nickel is more strain-rate sensitive at lower strain rates. ► Micro-crystalline nickel is more strain-rate sensitive in the phonon drag regime.