Influence of cooling rate on distortion and microstructure in extrusion of Al-Mg-Si alloys

Abstract

The technology of the curved profile extrusion (CPE) offers a potential for manufacturing of three dimensional curved profiles in one process by using a conventional die in combination with a generalized moveable guiding tool. To utilize the full potential of the CPE process for the production of lightweight construction components, particularly in regarding to the required mechanical properties and therefore the microstructure development, an embedded controlled quench system is necessary. A forced air quench system was designed, built and tested on extrusion of thin wall aluminum tubes. Homogeneous as well as partial quenching strategies were carried out in interaction with the CPE process. Manufacturing of straight profiles in a narrow range of tolerance is possible and unproblematic. In case of reproducible shape distortion thermally caused distortion can be compensated by deflection using the proposed CPE strategy. The cooling efficiency of the forced air quenching system was investigated by analyzing the microstructure and the mechanical properties of quenched profiles in different quenching and temper conditions. Using the process heat of extrusion for solution heating the formation of peripheral coarse grains in the alloy EN AW-6082 can be nearly eliminated at low ram speed. After aging, hardness and tensile strength were measured. Mechanical properties up to T4 and T6 temper conditions could be achieved by air quenching and aging.