Homogenisation Efficiency Assessed with Microstructure Analysis and Hardness Measurements in the EN AW 2011 Aluminium Alloy

Abstract

When extruding the casted rods from EN AW 2011 aluminium alloys, not only their homogenized structure, but also their extrudable properties were significantly influenced by the hardness of the alloy. In this study, the object of investigations was the EN AW 2011 aluminium alloy, and the effect of homogenisation time on hardness was investigated. First, homogenisation was carried out at 520 °C for different times, imitating industrial conditions. After homogenisation, the samples were analysed by hardness measurements and further characterised by microscopy and image analysis to verify the influence of homogenisation on the resulting microstructural constituents. In addition, non-equilibrium solidification was simulated using the program Thermo-Calc and phase formation during solidification was investigated. The homogenisation process enabled more rounded shape of the Al2Cu eutectic phase, equilibrium formation of the phases, and the precipitation in the matrix, leading to a significant increase in the hardness of the EN AW 2011 aluminium alloy. The experimental data revealed a suitable homogenisation time of 4–6 h at a temperature of 520 °C, enabling optimal extrusion properties.

Keywords

• EN AW 2011 aluminium alloy
• thermodynamic equilibrium
• intermetallic phases
• eutectic
• homogenisation
• hardness