Microstructural evolution of nanocrystalline chips particles produced via large strain machining during ball milling

Nanocrystalline Al 2014 alloy chips were produced from a T6 treated billet by using large strain machining as a severe plastic deformation technique. The chips were crushed and milled for 48 h. The microstructures and morphologies of the chips and their evolution during milling were characterized by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). From XRD investigations the grain sizes, microstrains and dislocation densities of the particles were evaluated. Also, microhardness measurements were performed to estimate the mechanical properties of the particles. It was found that the microhardness of Al 2014 particles increased with increasing the milling time. After milling to 48 h, the particle size reduced to 40 μm, the grain size reduced to 30 nm and the dislocation density increased to 11.5 × 1015 m− 2. Also, a fine dispersion of the precipitates was formed in the matrix of the as-milled particles.