Increasing the work hardening capacity of equal channel angular pressed (ECAPed) aluminum through multi-axial compression (MAC)

• Aluminum has a low strength that can be increased by lowering its grain size.
• Equal Channel Angular Extrusion (ECAP) lowers aluminum grain size.
• ECAP decreases drastically the work hardening rate and uniform ductility of aluminum.
• Multi Axial Compression (MAC) causes no change in dimensions and shape of specimens.
• MAC after ECAP increased the work hardening rate and uniform ductility of aluminum.

The low strength of commercial purity aluminum can be increased by solid solution, precipitation/aging, work hardening and grain size decrease. The latter has been extensively studied utilizing Severe Plastic Deformation (SPD), leading, however, to a negligible final uniform tensile ductility of the material due to its low or negative work hardening rates. Microstructural and compositional techniques have been used to partially circumvent this problem. Multi-axial compression (MAC) of previously compressed aluminum can soften the material and lead to increased work hardening capacity under ulterior monotonic compression. In the present research, MAC was applied to aluminum after SPD employing Equal Channel Angular Pressing (ECAP). The material softened after MAC, and its ulterior compression evolved with a much higher work hardening rate than in the absence of MAC, thus opening a new possibility of mechanically increasing the work hardening capacity and uniform ductility of aluminum (and other materials) after ECAP.