Enhanced tribological performance of nanotwinned copper enabled by sliding-induced heterostructure

Nanotwinned metals have many advantages such as high strength, reasonable ductility and high damage tolerance. However, studies on their tribological properties are scarce, especially the tribological performance relative to the counterparts with comparable hardness. Here, dry sliding tests of electrodeposited nanotwinned copper sample (NT-Cu) are carried out in comparison with the nanocrystalline copper (NC-Cu) and coarse-grained brass (CG-Br) samples that have similar initial hardness. Their worn surface morphologies, chemical compositions and worn subsurface microstructures are characterized in detail. At a load of 3 N, the friction coefficient of NT-Cu is 0.25, which is 44 % and 58 % lower than CG-Br and NC-Cu, respectively. The wear rate is 1.4 × 10 − 6 ( mm − 3 / Nm ) , which is 3.8 % of NC-Cu and 10.4 % of CG-Br, respectively. When the load is increased to 5 N, their difference in wear rate increases obviously. The superior tribological performance of NT-Cu is attributed to the sliding-induced layered heterostructure that can effectively accommodate frictional work and suppress the cracking and peeling-off of dynamic recrystallized structures.