Microstructure of a bulk nanocrystalline Al-Zn-Mg-Cu alloy prepared by cryomilling and spark plasma sintering

A bulk nanocrystalline Al-Zn-Mg-Cu alloy was produced by cryomilling and spark plasma sintering. The grain size, the microstrain, phase transformation and microstructure of this alloy were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the bulk nanocrystalline 7000 aluminum alloy prepared by spark plasma sintering has two types of distinctive nanostructures-primarily equiaxed grains with diameters of 50-100 nm, and a few of larger grains with diameters of 200-400 nm. The precipitate of second phases, mainly including η (MgZn₂) and a few θ (Al₂Cu) and S(Al₂CuMg), and recrystallization of the bulk nanocrystalline 7000 aluminum alloy were found during the consolidation process by SPS