Strengthening of Mg-Al-Ca alloys with C15 and C36 Laves phases

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 a-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 a-Mg matrix, at a-Mg/C36 and a-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 a-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 a-Mg/C36 and a-Mg/C15 composites.