Stabilization of nanocrystalline Cu by Al addition

Nanocrystalline Cu-14 at.% Al alloy was synthesised by cryomilling. Milled powder was then annealed up to T/Tm = 0.87 and corresponding changes in grain size (by X-ray peak broadening analysis) and hardness values were recorded. The hardness of the milled powder (3.28 GPa) decreases only ~ 17% (2.73 GPa) after annealing at T/Tm = 0.87. The improved thermal stability was attributed to the dispersion of nanoscale intermetallic (CuAl2) phase, observed by Transmission electron microscopy (TEM) investigation of the annealed samples. The closure agreement of theoretically estimated mechanical property (hardness) with the experimentally obtained one elicits kinetic stabilisation (i.e. grain boundary pinning by intermetallic particles) is the governing strengthening mode at high temperatures.