The present study investigates the effect of two different microstructural conditions on the hot deformation behavior of precipitation-hardenable AA7075 by compression tests ranging from 200 °C to 350 °C and strain rates from 0.1 s−1 to 10 s−1. The first condition is solution heat-treated and quenched in water, whereas the second condition is achieved by subsequent artificial aging and stabilization for 24 h at the respective intended deformation temperature. Both conditions indicate an increase in flow stress with increasing strain rate and decreasing deformation temperature. Moreover, with increasing deformation temperature and decreasing strain rate, the flow behavior gradually changes as dynamic recrystallization becomes the dominant factor for the flow curve appearance. At the same deformation temperature, higher flow stresses are obtained for the as-quenched condition due to the dynamic precipitation and growth of very small precipitates (r < 20 nm) during hot deformation. For the deformation temperature of 200 °C and the strain rate of 10 s−1, higher peak stresses of 110 MPa are obtained for the as-quenched condition. This is confirmed by the transmission electron microscopy investigations, which show the formation of very fine precipitates for the as-quenched condition, while coarse precipitates can be found in the stabilized microstructure. Despite this observation, the work hardening analysis reveals lower strain-hardening rates for the as-quenched condition and higher critical stresses for the onset of dynamic recrystallization compared to the thermally stabilized microstructure.

In this work, different friction models available in HyperXtrude had been investigated in the context of hot forward extrusion simulation of aluminum alloys. Extrusion trials were carried out for EN AW 6060 and EN AW 6082 at different temperatures and ram speeds. The extrusion forces as well as material temperatures near the exit of the die were recorded and used for the validation of the simulations. FE-simulations of each extrusion trial were carried out in HyperXtrude. Initially, friction models were calibrated for only two extrusion trials. Then, these calibrated friction models were used to simulate the extrusion trials with different process parameters. Reasonably good agreements were observed between experiments and simulations in terms of extrusion forces. However, the simulations overpredicted the material temperature by almost up to 40 °C for extrusion trials with high ram speed.

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The ferrite fraction and phase distribution of duplex steels depend strongly on the temperature evolution during hot deformation and are correlated to different mechanical behaviors during hot deformation as well as cold deformation. Therefore, the control of microstructure evolution during hot forming is relevant for target-oriented material design. In flow stress modelling for hot forming, the influence of microstructure beyond the ferrite fraction is often neglected. In the present work, a new method is demonstrated to also consider the influence of grain size in flow stress modelling. For this purpose, different initial microstructures with different ferrite fractions and phase distribution were tested in compression tests at 1100 °C and 0.1 s−1. The microstructure was analyzed before and after forming and it was observed that the differences in ferrite fractions vanished during the compression tests. Those microstructure data were used in a model including a rule of mixture and Hall–Petch relationship to extract the single-phase flow curves of ferrite and austenite. Based on the flow stress of the single phases, in combination with ferrite fraction and individual grain size, the flow curves of the different material conditions were calculated and the concurrent influence of ferrite fraction and phase distance on the mechanical behavior was discussed.

The creep resistance of light metals is of utmost relevance for application at elevated temperatures. This includes automotive components in power trains, engines, battery casings and transmission housings. The alloy design of temperature resistant light alloys for these applications depends heavily on the timely determination of the creep behavior. However, specialized facilities and testing equipment are required to perform creep experiments, which are not available in all labs. In contrast, deformation dilatometers are state-of-the-art at most research facilities with a metal forming department. These instruments can apply a constant force at high temperatures and are therefore, in principle, able to conduct creep experiments. To validate the applicability of such a deformation dilatometer for the development of magnesium alloys, short time creep experiments were conducted and compared with results from a standardized creep stand. Good agreement between the dilatometer and conventional constant force creep experiments was found. In this work, both methods are described in detail and possible limitations are discussed.