The Cu–30%Zn alloy was selected as a model material because it had a low stacking-fault energy of 7mJ/m2 and twinning was its predominant deformation mechanism. High-pressure torsion, equal channel pressing and equal channel pressing followed by rolling were used to achieve a wide range of grain size from about 3μm to 70nm. It was found that, with decreasing grain size, the average distance between deformation twins decreases gradually from 177nm to 24nm, while the density of deformation twins (the length of twin boundary in unit area) exhibit a maximum value at equal channel pressing +95% rolling sample with average grain size of 110nm. Careful statistics analysis reveals two optimum grain size ranges 60–80nm and 40–50nm for maximum twin density values for equal channel pressing +95% rolling and high-pressure torsion Cu–30%Zn samples, respectively. The underlying mechanisms governing the influence of grain size on twinning was discussed.

Influence of Grain Size on the Density of Deformation Twins in Cu–30%Zn Alloy. Y.Li, Y.H.Zhao, W.Liu, C.Xu, Z.Horita, X.Z.Liao, Y.T.Zhu, T.G.Langdon, E.J.Lavernia: Materials Science and Engineering A, 2010, 527[16-17], 3942-8