Significant enhancement in the thermal stability of nanocrystalline metals via immiscible tri-phases

The thermal stability of sputtered Co–Cu–Ag tri-phase immiscible nanocomposites (TPINs) was compared to nanocrystalline Cu50Ag50 and monolithic Cu. After annealing at 973 K, the grain size of Co34Cu33Ag33 was ∼115 nm, whereas that of Cu50Ag50 increased to over 700 nm. The hardness of annealed Co34Cu33Ag33 TPIN remained high, ∼3 GPa, comparing to only 1.0 GPa for Cu50Ag50 film. The remarkable thermal stability of the TPIN is largely achieved via the introduction of a third immiscible phase, forming abundant tri-phase triple junctions.