Influence of strain rate on the orientation dependence of microstructure in nickel single crystals

The deformation microstructures of nickel single crystals (99.945 wt.%) during dynamic plastic deformation and quasi-static compression to a true strain of 0.20 were comparatively investigated. The deformation microstructures are orientation dependent, forming cell structure, slip plane aligned or not slip plane aligned extended boundaries. It is found that the orientation spread decreases, remains unchanged and becomes enhanced when loading along 〈0?0?1〉, 〈0?1?1〉 and 〈1?1?1〉, respectively, as strain rate increases.     

Effect of heat treatment on the microstructure and mechanical properties of spray-formed 7055 aluminium alloy

7055 Al alloys samples were prepared by spray forming and hot-extrusion followed by two different aging treatment procedures. Their different distributions of GP zones, and nanoscale precipitates η′ (MgZn) and η (MgZn₂) are extensively investigated by transmission electron microscope (TEM). The mechanical properties, including tensile strength, Vickers hardness and elongation of both aged 7055 Al alloys, have also been measured and analysed. It is found that T6 and T76 aging treatment results in quite different microstructure and mechanical properties. The outstanding performance of the 7055 Al alloys after T6 aging treatment is attributed to nanoscale semi-coherent dispersion precipitates.