No abstract

Lean alloyed Mg-Al-Ca alloys reveal weakened basal-type texture intensities and increased room-temperature ductility when compared to pure Mg. Since the combined effects of the alloying elements Al and Ca on texture evolution are not yet fully understood, in this study, two binary and seven ternary Mg-Al-Ca alloys (ranging between 0–2 wt.-% Al and 0–0.5 wt.-% Ca) were subjected to cold rolling with texture measurement after each rolling step. These measurements showed that the basal-type texture of Mg is weakened by the addition of Ca, while the addition of Al leads to stronger basal-type textures compared to the samples containing Ca. The joint effect of Al and Ca can, for specific alloy compositions, lead to a steady-state basal texture intensity, which does not become stronger with further rolling. We expect that the solubility limit of Ca in Mg affects this behaviour. For comparison, mechanical properties were obtained by compression testing, showing high degrees of deformation, of 15–25%.

Laves phases such as CaMg2 (C14), Ca(Al,Mg)2 (C36), and CaAl2 (C15) have high melting points, high hardness at room and elevated temperatures, but are inherently brittle. Cast Mg–Al–Ca alloys having Laves phase skeleton thus have good creep properties but limited ductility. An understanding of the co-deformation behaviour of α-Mg and Laves phases is essential for further improving the mechanical performance of these alloys. Here, we study the mechanical behaviour of a Mg–4.65Al–2.82Ca alloy using micropillar compression in the α-Mg matrix, at α-Mg/C36 and α-Mg/C15 interfaces and in the C15 phase in combination with scanning electron microscopy. We show that both, C15 and C36 phases, provide considerable strengthening to the α-Mg matrix. The amount of strengthening primarily depends on the volume fraction and geometry of Laves phases in composite micropillars and correlates well with the iso-strain and iso-stress bounds predicted for α-Mg/C36 and α-Mg/C15 composites. Graphical Abstract