Co-deformation between the metallic matrix and intermetallic phases in a creep-resistant Mg-3.68Al-3.8Ca alloy

• Main Authors: M. Zubair, S. Sandlöbes-Haut, M. Lipińska-Chwałek, M.A. Wollenweber, C. Zehnder, J. Mayer, J.S.K.-L. Gibson, S. Korte-Kerzel
• Format: Article
• Language: English
• Published: Elsevier 2021-11-01
• Series: Materials & Design
• Subjects: Electron microscopy; Mg alloy; Mechanical properties; Micro-/nanoindentation; Co-deformation
• Online Access: http://www.sciencedirect.com/science/article/pii/S0264127521006687

The microstructure of Mg-Al-Ca alloys consists of a hard intra- and intergranular eutectic Laves phase network embedded in a soft α-Mg matrix. For such heterogeneous microstructures, the mechanical response and co-deformation of both phases under external load are not yet fully understood. We therefore used nano- and microindentation in combination with electron microscopy to study the deformation behaviour of an Mg-3.68Al-3.8Ca alloy.We found that the hardness of the Mg2Ca phase was significantly larger than the α-Mg phase and stays constant within the measured temperature range. The strain rate sensitivity of the softer α-Mg phase and of the interfaces increased while activation volume decreased with temperature. The creep deformation of the Mg2Ca Laves phase was significantly lower than the α-Mg phase at 170 °C. Moreover, the deformation zone around and below microindents was dependant on the matrix orientation and was influenced by the presence of Laves phases. Most importantly, slip transfer from the α-Mg phase to the (Mg,Al)2Ca Laves phase occurred, carried by the basal planes. Based on the observed orientation relationship and active slip systems, a slip transfer mechanism from the soft α-Mg phase to the hard Laves phase is proposed. Further, we present implications for future alloy design strategies.