Size-dependent mechanical properties and deformation mechanisms in Cu/NbMoTaW nanolaminates

High entropy alloys (HEAs) have attracted extensive attention due to their excellent properties in harsh environments. Here, we introduced the HEA NbMoTaW into the laminated structure to synthesize the Cu/HEA nanolami-nates (NLs) with equal layer thickness h spanning from 5 to 100 nm, and comparatively investigated the size dependent mechanical properties and plastic deformation. The experimental results demonstrated that the hardness of Cu/HEA NLs increased with decreasing h, and reached a plateau at h ≤ 50 nm, while the strain rate sensitivity m unexpectedly went through a maximum with reducing h. The emergence of maximum m results from a transition from the synergetic effect of crystalline constituents to the competitive effect between crystalline Cu and amorphous-like NbMoTaW. Micro-structural examinations revealed that shear banding caused by the incoherent Cu/HEA interfaces occurred under severe deformation, and the soft Cu layers dominated plastic deformation of Cu/HEA NLs with large h.