Extended twins, up to 100nm in length and occupying the length of an entire grain, were observed in an Al–4%Mg alloys/B4C nanocomposite material processed via high-temperature, high-strain-rate forging. High-resolution electron microscopy, used to identify the extended twins and to formulate the mechanism for their formation, indicates that they were created by the emission of 1/6<112> twinning partial dislocations. The macroscopic origin was attributed to the local high stress field present during the forging process.

Extended Twinning Phenomena in Al–4%Mg Alloys/B4C Nanocomposite. Y.Li, Y.J.Lin, Y.H.Xiong, J.M.Schoenung, E.J.Lavernia: Scripta Materialia, 2011, 64[2], 133-6