Extended twinning phenomena in Al–4%Mg alloys/B4C nanocomposite

Extended twins, up to 100 nm in length and occupying the length of an entire grain, are 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 are created by the emission of 1/6〈1 1 2〉 twinning partial dislocations. The macroscopic origin is attributed to the local high stress field present during the forging process.