Laves phases in Mg-Al-Ca alloys and their effect on mechanical properties

•Laves phases are designed in Mg-Al-Ca alloys in three crystal structures, as interconnected networks and dispersed particles depending on the heat treatment.•The Laves phases in equilibrium with Mg matrix have composition in agreement with Calphad modelling. New compositional ranges of Laves phases were determined from non-equilibrium microstructures.•Semi-coherent and incoherent interfaces between Laves phases and the Mg matrix were revealed by high resolution electron microscopy.•The ductility of the alloys is significantly improved by annealing. Their yield strengths depend on the interconnectivity and inter-particle spacing of the Laves phases.