Microstructural stability of copper with antimony dopants at grain boundaries: experiments and molecular dynamics simulations

This study presents evidence that the microstructural stability of fine-grained and nanocrystalline Cu is improved by alloying with Sb. Experimentally, Cu100−xSbx alloys are cast in three compositions (Cu-0.0, 0.2, and 0.5 at.%Sb) and extruded into fine-grained form (with average grain diameter of 350 nm) by equal channel angular extrusion. Alloying the Cu specimens with Sb causes an increase in the temperature associated with microstructural evolution to 400 °C, compared to 250 °C for pure Cu. This is verified by measurements of microhardness, ultimate tensile strength, and grain size using transmission electron microscopy. Complementary molecular dynamics (MD) simulations are performed on nanocrystalline Cu–Sb alloy models (with average grain diameter of 10 nm). MD simulations show fundamentally that Sb atoms placed at random sites along the grain boundaries can stabilize the nanocrystalline Cu microstructure during an accelerated annealing process.