Experimental investigation of the effects of preheating temperature changes on hardness after the ageing process of aluminium alloys AA6060 produced by extrusion using two-figured die

Among aluminium alloys, AA6060 series alloys are one of the alloy types widely used in extrusion production. Aluminium alloys are preferred in industrial practise due to their low density, high thermal conductivity, ease of manufacturing, high electrical conductivity and superior corrosion resistance. Preheating temperature, which is among the most important variable parameters of the extrusion process, plays a role in improving the visual and mechanical properties of AA6060 alloys. In this study, the effect of preheating temperature variation on the hardness of a 2-figure hollow profile produced by extrusion method using AA6060 alloy was investigated. During the study, the samples were artificially aged at 185 °C for 300 minutes and the microstructure was assessed using an optic microscope. The highest hardness results were measured at 430,3 °C (59,07 HB for figure 1, 58,71 HB for figure 2) and 440,2 °C (60,14 HB for figure 1, 57,78 HB for figure 2). Thus, it is shown that there is practically no benefit in increasing the preheating temperatures after 440,2 °C for the die figures used in this study. When evaluating the hardness of the test samples, it was found that the hardness values of all samples were above 55 HB. Thus, the value range for machinability (55-70 HB) is provided. As a result of the microstructure investigations, it was determined that the Mg2Si phase, which increases the hardness of AA6060 alloy, is homogeneous.