Samples of pure Cu and a Cu–10%Zn alloy were processed by high-pressure torsion and by high-pressure torsion, followed by cold-rolling to a reduction of about 75%. The grain sizes in these 2 conditions were measured by transmission electron microscopy and by X-ray diffraction. The experimental results showed that the average grain size and the width of the grain size distribution were both smaller in the Cu–10%Zn alloy by comparison with pure Cu. This difference was due to the lower stacking fault energy of the Cu–10%Zn alloy. An analysis showed all of the experimental results were consistent with a theoretical model which predicted the minimum grain size produced by milling.

Influence of Stacking Fault Energy on the Minimum Grain Size Achieved in Severe Plastic Deformation. Y.H.Zhao, Y.T.Zhu, X.Z.Liao, Z.Horita, T.G.Langdon: Materials Science and Engineering A, 2007, 463[1-2], 22-6