In this work, an attempt has been made to improve mechanical properties of 6063 aluminium alloy via combination of heat treatment (precipitation hardening) and severe plastic deformation by hydrostatic extrusion (grain size refinement). Samples were extruded in hardened (T66) and supersaturated states. The samples extruded directly after quenching were additionally subjected to aging process. The influence of aging parameters such as time and temperature on mechanical properties evolution of extruded material was determined.

6063 aluminium alloy was chosen as the best material for lightweight structures, where mass reduction is important, using Ashby`s maps and market analysis. Traditionally 6063 AA is formed by hot extrusion. In this work, the alloy was hydrostatically extruded at ambient temperature in order to obtain ultrafine grained structure. Microstructural changes after every stage of extrusion was observed with optical microscope. Microstructure of ultrafine grained alloy was investigated using transmission electron microscopy. The average grain diameter and grain boundary misorientation angles (using Kikuchi`s lines) were measured. Mechanical properties were examined in microhardness test and tensile test.

The results have shown that the highest mechanical strength was obtained for a sample extruded in hardened T66 condition but its ductility was poor. Ageing at 100°C for 26 hours of samples extruded previously solution treatment and quenched results in an increase of mechanical properties (compared to extrusions without ageing) but yield strength is still lower than measured for material extruded in hardened condition. On the other hand, this sample exhibits substantially improved ductility which make it attractive for lightweight applications.

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