In this project, we aim to enhance the mechanical properties of an equiatomic CoCrNi medium-entropy alloy (MEA) by interstitial alloying. Carbon and nitrogen with varying contents have been added into the face-centred cubic structured CoCrNi MEA. The introduction of interstitial atoms results in considerably more pronounced strengthening effect in the MEA compared to that without interstitial addition. The underlying mechanisms are mostly associated with the interactions between interstitials and dislocations.
Equiatomic CoCrNi MEA attracted considerable attention due to its excellent combination of mechanical strength, ductility and fracture toughness. We explore the idea of incorporating additional interstitial elements to further boost its properties. The mechanisms responsible for the strengthening effect are related to the different manner interstitials interact with dislocations, as compared to larger substitutional atoms. While the latter are able to interact only with edge dislocation (due to symmetrical spherical distortion they produce), the interstitials interact with both types of dislocations, i.e. edge and screw dislocations, as a consequence of tetragonal distortion and resulting shear stress. Other phenomena of interstitial atoms presence like the change in stacking fault energy (SFE) may also come into play, changing the way plastic deformation is mediated. Also, the interstitial alloying can significantly alter the recrystallization kinetics according to the fact that the interstitial-free CoCrNi MEA can be fully recrystallized while the interstitial MEA containing 0.5 at. % C retains deformed microstructure after an identical annealing process.
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
Enabling a ‘hydrogen economy’ requires developing fuel cells satisfying economic constraints, reasonable operating costs and long-term stability. The fuel cell is an electrochemical device that converts chemical energy into electricity by recombining water from H2 and O2, allowing to generate environmentally-friendly power for e.g. cars or houses…
This project is part of Correlative atomic structural and compositional investigations on Co and CoNi-based superalloys as a part of SFB/Transregio 103 project “Superalloy Single Crystals”. This project deals with the identifying the local atomic diffusional mechanisms occurring during creep of new Co and Co/Ni based superalloys by correlative…