This study compares AZ91 with AZ31 to investigate the influence of a higher Al content on the resulting microstructure, mechanical properties, and hot deformation behavior. While AZ31 exhibits a globular structure after casting, AZ91 shows a fully developed dendritic structure due to the promotion of dendrites. A heat treatment helped to homogenize AZ31, dissolved a large part of the Mg-Al precipitations in AZ91, and formed globular grains in AZ91. Due to the impact of Al on constitutional supercooling, AZ91 exhibits smaller grains than AZ31. Because of the strengthening of the solid solution, AZ91 also exhibits higher strength and hardness compared to AZ31. Cylindric compression tests of the heat-treated samples were conducted at different temperatures (300–400 °C) and strain rates (0.1 × 10 s⁻¹). The main dynamic recrystallization (DRX) mechanisms in AZ31 and AZ91 are twinning-induced DRX and discontinuous DRX. It was detected that Mg₁₇Al₁₂ precipitates at the grain boundaries in AZ91, which influences the grain size through pinning. Similar results could be conducted in rolling trials. Although both alloys have similar grain sizes after rolling, AZ91 exhibits higher strengths, while AZ31 shows higher ductility. This can be explained by the solid solution strengthening in AZ91 and less brittle Mg₁₇Al₁₂ precipitations in AZ31.

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.

Since 2018, the institute of metal forming has been studying the novel twin-roll casting (TRC) of magnesium wire at the pilot research plant set up specifically for this purpose. Light microscopic and scanning electronic investigations were carried out within this work and show the unique microstructure of twin-roll cast AZ31 magnesium alloy with grain sizes of about 10 μm ± 4 μm in centre and 39 μm ± 26 μm near the surface of the sample. By means of a short heat treatment (460 °C/15 min), segregations can be dissolved and grain size changes in centre to 19 μm ± 12 μm (increase) and near the surface to 12 μm ± 7 μm (decrease). Further, the mechanical properties of the twin-roll cast and heat-treated wire were analysed by tensile testing at room temperature. By heat treatment, the total elongation could be increased by a third whereas the strength decreases slightly. In heat-treated state, no preferred orientation is evident. In addition to the twin-roll cast and the heat-treated condition, the rolled state was analysed. For this purpose, the twin-roll cast wire was hot rolled using an oval-square calibration. After hot rolling, a dynamic recrystallization and grain refinement of the twin-roll cast wire could be achieved. It can be seen, that an increase in strength as well as in total elongation occur after wire rolling. Beside this, a rolling texture is evident.

In order to meet customer requirements, technology developments need to stay focused at process rationalization and quality improvements. Combining the twin-roll casting technology and caliber rolling technology for magnesium wire, customer demands concerning cost-efficiency and high quality can be satisfied. The resulting long products can be applied in the automotive industry and aircraft sector as joining and welding elements or in biomedicine as screws. For this purpose, the paper analyzes potential application fields and their induced quality properties. Special requirements of illustrative magnesium long products are shown by adapting existing requirements of aluminum wire. Finally, the innovative magnesium wire production technology will be explained and the advantages, in particular the resource efficiency, of the developed technology will be discussed.

Due to a combination of casting and rolling in one process step, twin-roll casting is an effective grain refinement method. This study compares the direct-chill cast (DC) state and the twin-roll cast (TRC) state of an AZ31 magnesium alloy in different steps regarding the microstructure, deformation behavior, and mechanical properties. In the initial state, the TRC AZ31 exhibits a significantly finer grain size and a slight rolling texture compared to the DC AZ31. Therefore, the TRC materials exhibit higher strengths and ductility. After a short heat treatment of 400 °C and 12 h for the DC state and 460 °C and 15 min for the TRC state, cylindric compression tests of the heat-treated samples were conducted at different temperatures (300–400 °C) and strain rates (0.1–10 s⁻¹). To reproduce the deformation behavior at higher strain rates, hot rolling tests (350 °C, 15 s⁻¹) of the heat-treated samples were performed. For both alloys, discontinuous dynamic recrystallization and twinning-induced dynamical recrystallization could be detected. A fine grain size and similar strengths were present after five passes. The AZ31 TRC exhibited a higher ductility due to a higher texture intensity, as the stress direction corresponds to the rolling direction in the case of tensile testing.