Effect of extrusion processing on the microstructure and mechanical properties of AA6082 aluminium alloys

The growing demand for the use of moderate strength Al-Mg-Si aluminium alloys for the structural components in diverse engineering fields has necessitated efforts by extruders to address the structural challenges associated with extrusion practice. The aim of this project is to study the effect of billet preheating, cooling media, extrusion exit speed and ageing on the microstructure and mechanical properties of Al-Mg-Si (AA6082) alloys. The investigation of the effects has been carried out with the aid of differential scanning calorimetry, light and scanning electron microscopy to track the microstructural evolution during the different extrusion processes. The mechanical properties were assessed using hardness and tensile testing. The results of the experiment showed that there is an improvement in the mechanical properties at higher exit speed. The optimum mechanical properties (hardness, tensile strength and elongation) were obtained when extrusion was preceded by a billet pre-heating temperature of 500°C, at an exit speed of 16m/min and water-cooled during the extrusion, aged at 175°C for 6hours. Also, prior extrusion process remarkably impacted the ageing response and final mechanical properties of the alloy. The implication of this findings is that, extruders can enhance both mechanical properties and productivity using a lower press capacity given that the surface quality is within the allowable windows.