Athanasios Vazdirvanidis, Sofia Papadopoulou, Grigoris Symeonidis, Fivos Aslanis, Andreas Rikos and Eva Stachouli
Abstract: In the current investigation, the effect of cooling rate after extrusion on the mechanical properties and the microstructure of 6061 alloy extruded profiles for the automotive industry is examined. Water quenching, air cooling and step-cooling (combination of air cooling and water quenching) are performed after solution heat treatment for simulating different cooling processes on the exit of the extrusion press. Microstructure examination is performed after artificial aging for each cooling method accompanied by 3-point bending and tensile testing for investigation of differences in formability characteristics. Electron fractography, texture and grain boundary misorientation analysis were used as analytical techniques for the determination of susceptibility to crack initiation and correlation between texture and cracking behaviour during mechanical testing. From the examination, the positive role of rapid cooling for improved formability is highlighted. Also, through the grain boundary misorientation analysis and the formation of Taylor factor maps it is shown that in the more ductile samples formation of discontinuities is preferably taking place at subsurface regions even though “roughening” of the bent surface is obvious and expected to lead to crack initiation. The results of this project will be used for optimization of the automotive extruded profiles production process ensuring improved mechanical performance and resistance to premature fracture.