A05 – Generalised deformation mechanism maps and dislocation defect phase interactions with vacancies in Laves phases

PI: Prof. Dr. Sandra Korte-Kerzel (RWTH Aachen University, Institute for Physical Metallurgy and Materials Physics), Dr.-Ing. Zhuocheng Xie (RWTH Aachen University, Institute for Physical Metallurgy and Materials Physics)

SFB researchers: Sang-Hyeok Lee (RWTH Aachen University, Institute for Physical Metallurgy and Materials Physics)

During the first funding period, we investigated the active slip systems and their critical stresses for dislocation glide in several complex crystals within the Mg-Al-Ca system, specifically the CaAl₂, Ca(Mg,Al)₂, and CaMg₂ Laves phases, as well as the Mg₁₇Al₁₂ phase. Plasticity was achieved using nanomechanical testing methods such as nanoindentation and micropillar compression testing at room and elevated temperatures. By analyzing mechanical properties and slip planes through statistical slip trace analysis around indentations, correlated with orientation information from EBSD measurements, we calculated the critical resolved shear stress. A significant finding was the identification of the {112} plane as the main slip plane at low temperatures in the cubic C15 phase. We discovered that alloying CaAl₂ with Mg results in a pronounced transition of the dominant slip plane towards the {112} planes, while the similar slip plane transition effect is observed in the hexagonal CaMg₂ phase.

While the first funding period ended successfully with key findings such as the newly reported {112} slip plane and the effect of point defects on the plastic deformation of Laves phases, we aim to provide a more general understanding of dislocation defect phases in Laves phases by observing changes in plasticity with varying stoichiometry and temperature. In particular, we will investigate the underlying mechanisms and barriers to dislocation motion as a function of atomic radius ratios and the presence of point defects, especially vacancies. To this end, we will combine the computational approach (nudged elastic band and stacking fault energy calculation) using the DFT-based machine learning potential and the experimental approach (room/high temperature indentation, pillar compression, and TEM investigation) to understand the radius ratio (ra/rb) and dislocation-point defect interactions. 

Furthermore, we aim to produce maps of defect phase mechanisms and properties that link microscale data at room temperatures with macroscale data at high temperatures. In this way, we will not only deepen our understanding of deformation in these complex crystals, but also able to provide the generally applicable insights into the active defect phases and their transitions with alloying or element substitution and temperature.