In the present work, the microstructure and texture of a Mg–6.8Y–2.5Zn–0.4Zr sheet manufactured by twin-roll casting were investigated. The twin-roll cast state consisted of two apparent phases: the α-Mg matrix, which was made up of dobulites with an average grain size of approximately 50 µm and the LPSO (long-period stacking ordered) phase, which formed network-like precipitates along the grain boundaries. After twin-roll casting, annealing was carried out under conditions of different temperatures ranging from 450 °C to 525 °C and holding times between 2 h and 24 h. It was found that heat treatment led to the formation of a microstructure in which grains were apparent. Furthermore, it could be observed that high temperatures > 500 °C led to changes in the morphology of the LPSO structures. On one hand, the network-like structure dissolved while, on the other hand, both rodlike and blocky LPSO phases precipitated predominantly at the grain boundaries of the α-Mg matrix. This process was fostered by high temperatures and long holding times.

Due to their low density and high specific strength, magnesium alloys offer great potential as a design material for lightweight construction. An economical and energy-efficient method for the production of magnesium wire is the technology of twin-roll casting. In this work, the deformation behaviour of twin-roll cast and heat-treated AZ31 wire pre-profile is investigated for the first time during the compression test at different temperatures (250–400 °C) and forming speeds (0.01–10 s⁻¹). To obtain optimal parameters, a processing map is created, and the microstructural changes during the hot forming processes are determined by accompanying microstructure characterization through an optical microscope and scanning electron microscope. The heat treatment causes a reduction in segregation and a homogeneous microstructure. The average activating energy for plastic deformation of twin-roll cast and heat-treated magnesium alloy AZ31 is 159.008 $\mathrm{kJ}·{\mathrm{mol}}^{-1}$. The instability region of the process map starts at a forming temperature of 250 °C and extends into the range of high forming speeds (1–10 s⁻¹). In this area, cracks in the microstructure can be detected during hot forming. At high temperatures (300–350 °C), dynamic recrystallization at the grain boundaries is observed as the main forming mechanism. Based on these results and observations, existing models for describing the hot forming behaviour of magnesium alloys can be extended and validated.