Microstructure, creep and strain partitioning of Mg-Al-Ca alloysWednesday (26.09.2018) 15:15 - 15:30 S1/01 - A4 Part of:
Weight reduction in the automotive and aerospace industry is one of the key elements to improve fuel efficiency and reduce harmful emissions. Due to its low density of ~ 1.7 g cm–3, Mg has a high potential as a lightweight material in automobiles and aerospace applications. The most widely used Mg alloys in automobiles are Al containing Mg alloys e.g. AZ or AM series. However, the operating temperature of these alloys is limited to below 125°C due to rapid deterioration of their strength at elevated temperature. This is because the main strengthening phase present in Mg-Al based alloys is the Mg17Al12 intermetallic phase, which readily softens at elevated temperatures. Ca addition to these alloys can significantly improve their high temperature properties, e.g. creep resistance. Ca addition to Mg-Al alloys alters their microstructure by replacing the discontinuous Mg17Al12 phase with a continuous network of Laves phases, which in turn improves the creep resistance. The amount, type and distribution of Laves phases in Mg-Al-Ca alloys can be controlled by adjusting the Ca/Al ratio. In the present work, the influence of the Ca/Al ratio on the microstructure, creep properties and deformation behaviour of Mg-Al-Ca alloys has been investigated using SEM, uniaxial creep testing and quasi in-situ deformation experiments. The creep properties of individual phases have additionally been studied using nanoindentation. Moreover, the strain distribution at microstructural level occurring during high temperature tensile deformation is also measured using digital image correlation in quasi in-situ experiments inside the SEM.