Five-fold deformation twins were formed in an ultrafine grain, with a size of about 100nm, of a Cu–16at%Al alloy processed by high-pressure torsion. Formation occurred through the sequential emission of partial dislocations from grain boundaries and other multiple twin boundaries. These observations confirmed the emission of partial dislocations from multiple-fold nodes which could be attributed to increased twinnability via the introduction of Al atoms which lower the driving force for partial emission.

Formation of Fivefold Deformation Twins in an Ultrafine-Grained Copper Alloy Processed by High-Pressure Torsion. X.H.An, Q.Y.Lin, S.D.Wu, Z.F.Zhang, R.B.Figueiredo, N.Gao, T.G.Langdon: Scripta Materialia, 2011, 64[3], 249-52