Intrinsic size-controlled strain hardening behavior of nanolayered Cu/Zr micropillars

The strain hardening behavior of nanolayered Cu/Zr micropillars was studied using the microcompression technique, which revealed that both the strain hardening exponent and the strain hardening rate are controlled by the intrinsic rather than extrinsic size. The maximum strain hardening rate is observed at a layer thickness of ∼20 nm, which can be explained physically in terms of reduced dislocation storage rates. A dislocation model is modified to elucidate the dislocation storage in the nanolayered materials and predicts a critical intrinsic size below which the strain hardening rate drops off.