Preliminary Investigations into the Possibility of Using Hot Torsion Testing to Model Microstructural Evolution During Aluminum Extrusion

This paper outlines preliminary findings from studies on the possibility of using hot torsion testing for the physical modeling of microstructural evolution during aluminum alloy extrusion processes. Accordingly, two plastic deformation processes were investigated: high-temperature torsion and extrusion. The studies were conducted within the temperature range characteristic of the extrusion of 16 mm diameter round profiles made of EN AW-6060 aluminum alloy, with different cooling rates after deformation. Physical modeling of both processes was preceded by numerical modeling with the finite element method (FEM) and a detailed analysis of the deformation conditions occurring during both processes. Thanks to the careful selection of thermoplastic forming parameters, comparable values of the strain, strain rate, and temperature of profiles suitable for direct microstructural comparison were obtained. The conducted studies made it possible to determine the influence of the applied thermoplastic forming parameters on the microstructural evolution of the tested material. Finite element method simulations revealed distinct strain gradients in both the hot torsion and extrusion processes. Metallographic analysis of the EN AW-6060 alloy showed a strong dependence of grain size and the degree of recrystallization on the thermoplastic processing temperature and the local strain level. The obtained results confirm that hot torsion testing, combined with the selection of representative regions based on FEM analysis, can serve as a supporting method for modeling microstructural evolution in industrial extrusion processes, provided that the thermomechanical conditions correspond to those occurring in the modeled process.