The effects of room temperature ECAP and subsequent aging on the structure and properties of the Al-3%Mg aluminium alloy

- Microstructure of the ECAPed Al-3%Mg alloy is investigated by LOM, SEM and TEM.
- X-ray diffraction was used to calculate micro strain and dislocation density.
- Correlation between the obtained microstructure and mechanical properties is discussed.

The results of the present investigation are focused on the structure examinations of a commercial Al-3%Mg alloy in different conditions using an optical microscope (OM), scanning electron microscopy (SEM), the EBSD technique, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Measurements of the microhardness and ultimate tensile strength were carried out to evaluate the influence of ECAP and post-ECAP treatment on the mechanical properties. In this study, we found that 6 ECAP passes via route Bc result in a significant grain refinement. The measured average grain size of the as deformed sample was about 0.43 μm. As a result of the performed post-ECAP heat treatment (artificial ageing), a material with a more homogenous microstructure, having an average grain size of ~ 0.68 μm, was obtained. The results of the mechanical property measurements show a significant increase in mechanical strength to about ~ 384 [MPa] in the T9 condition and to ~ 330 [MPa] after post-ECAP treatment (T8 condition). The high strength of the alloy in the T9 condition is suggested to be related to grain size strengthening, dislocation strengthening and precipitation strengthening. An increase in elongation/ductility from 2.4% to 11.2% was observed in the T8 condition sample, which is a result of the grain growth and the dislocation density decrease.