Mechanical Properties and Nanostructure of Multi-Layered Al–Zn–Mg Alloy with Compositional Gradient

Abstract

The mechanical properties and nanostructure of the multi-layered aluminum alloy sheet were investigated by tensile test, hardness test, electron probe microanalysis and micro-small-angle X-ray scattering in scanning mode, focusing on the distributions through the thickness. The multi-layered sheets consisting of highly concentrated Al–Mg and Al–Zn alloys show a remarkable increase in proof stress after interdiffusion and artificial aging. The predominant layers to contribute to the proof stress change from the layers with higher Zn/Mg ratio in T4 temper to the layers with lower Zn/Mg ratio after artificial aging. These age-hardening responses depend on the layers, which are large in the layers with higher Zn/Mg ratio, whereas small in the layer with lower Zn/Mg ratio. These noticeable bulk properties are ascribed to the local change in the types, volumes and morphologies of the G.P. zones and/or metastable phases depending on the concentration profiles through the thickness, which are produced from these unique multi-layered structures.