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
This project (B06) is part of the SFB 1394 collaborative research centre (CRC), focused on structural and atomic complexity, defect phases and how they are related to material properties. The project started in January 2020 and has three important work packages: (i) fracture analysis of intermetallic phases, (ii) the relationship of fracture to…
Scandium-containing aluminium alloys are currently attracting interest as candidates for high-performance aerospace structural materials due to their outstanding combination of strength, ductility and corrosion resistance. Strengthening is achieved by precipitation of Al3Sc-particles upon ageing heat treatment.