Extrinsic size effect in microcompression of polycrystalline Cu/Fe multilayers

Microcompression tests of Cu/Fe multilayers with diameters ranging from 0.6 to 2.0 μm show that the flow stress increases with increasing pillar diameter, which implies that “larger is stronger”. Finite element analysis results explain the stress and strain distributions in the pillars, and suggest that the dimensional constraint is responsible for the strengthening. This work reveals a new mechanism of extrinsic size effect in polycrystalline multilayer pillars, which is opposite to the extrinsic size effect in single-crystal pillars.