In the present work, the microstructure, texture, mechanical properties as well as hot deformation behavior of a Mg-2Zn-1Al-0.3Ca sheet manufactured by twin roll casting were investigated. The twin roll cast state reveals a dendritic microstructure with intermetallic compounds predominantly located in the interdendritic areas. The twin roll cast samples were annealed at 420 °C for 2 h followed by plane strain compression tests in order to study the hardening and softening behavior. Annealing treatment leads to the formation of a grain structure, consisting of equiaxed grains with an average diameter of approximately 19 µm. The twin roll cast state reveals a typical basal texture and the annealed state shows a weakened texture, by spreading basal poles along the transverse direction. The twin roll cast Mg-2Zn-1Al-0.3Ca alloy offers a good ultimate tensile strength of 240 MPa. The course of the flow curves indicate that dynamic recrystallization occurs during hot deformation. For the validity range from 250 °C to 450 °C as well as equivalent logarithmic strain rates from 0.01 s−1 to 10 s−1 calculated model coefficients are shown. The average activation energy for plastic flow of the twin roll cast and annealed Mg-2Zn-1Al-0.3Ca alloy amounts to 180.5 kJ/mol. The processing map reveals one domain with flow instability at temperatures above 370 °C and strain rates ranging from 3 s−1 to 10 s−1. Under these forming conditions, intergranular cracks arose and grew along the grain boundaries.

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.

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Das Teilprojekt B3 des SFB 692 hat sich zum Ziel gesetzt, Aluminium/Magnesium‐Verbunde hinsichtlich seiner mechanischen Festigkeitseigenschaften und bruchmechanischen Kenngrößen zu analysieren. Des Weiteren soll die entstandene Grenzschicht in einem numerischen Modell abgebildet werden. Im folgenden Artikel werden die wesentlichen Erkenntnisse des Teilprojektes dargelegt. Es wurden verschiedene Faktoren untersucht, welche die Eigenschaften der Grenzschicht beeinflussen. Es zeigt sich, dass die Verbundqualität und die Festigkeit der Grenzschicht von einer Reihe von Größen abhängen, die maßgeblich im Prozess der Halbzeugherstellung, dem hydrostatischen und indirekten Strangpressen, begründet sind. Wird eine qualitativ einwandfreie Grenzschicht zwischen beiden Verbundpartnern erzeugt, weist dieses Interface eine hohe Festigkeit auf. Darüber hinaus wird gezeigt, wie sich die Verbunde in verschiedenen Temperaturbereichen unter Belastung verhalten. Des Weiteren wird das Versagensverhalten des Verbundes numerisch abgebildet.

Deformation behavior of an as-cast Mg-6.8Y-2.5Zn-0.4Zr alloy during plane strain compression was characterized in present work by high-temperature testing. Based on the experimental data, the values of strain rate sensitivity, efficiency of power dissipation and the instability parameter under the condition of various hot working parameters were investigated. Processing maps were established by superimposing the instability map over the power dissipation map, this being connected with microstructural evolution analysis in the hot deformation processes. Accompanied microstructure characterization of the binary α-Mg/ Long Period Stacking Ordered (LPSO) microstructure reveals that the flow behavior is related to the deformation mechanisms. At lower temperatures (350 – 400 °C) formation of kink bands is observed, which normally occur when deformation twinning is inhibited and other slip systems are strongly hindered by the complex LPSO structures. Dynamic recrystallization (DRX) was initiated at higher temperatures above 400 °C, influencing the softening behavior of the material significantly. DRX was the main softening mechanism when deformation takes place at 500 °C and the kink band deformation decreased.