Abstract: Complex multi-element alloys are gaining prominence for structural applications, supplementing steels, and superalloys. Understanding the impact of each element on alloy surfaces due to oxidation is vital in maintaining material integrity. This study investigates oxidation mechanisms in these alloys using a model five-element equiatomic CoCrFeNiMn alloy, in a controlled oxygen environment. The oxidation-induced surface changes correlate with each element’s interactive tendencies with the environment, guided by thermodynamics. Initial oxidation stages follow atomic size and redox potential, with the latter becoming dominant over time, causing composition inversion. The study employs in-situ atom probe tomography, transmission electron microscopy, and X-ray absorption near-edge structure techniques to elucidate the oxidation process and surface oxide structure evolution. Our findings deconvolute the mechanism for compositional and structural changes in the oxide film and will pave the way for a predictive design of complex alloys with improved resistance to oxidation under extreme conditions.
I don't know the background, but apparently someone named Cantor inspired the study of multi-component alloys.Baluncore said:With so many truths, and so many viewpoints and interactions for analysis,
Abstract
Multicomponent high-entropy Cantor alloys are single-phase and near-single-phase face-centred cubic alloys, occupying an enormous region of multicomponent phase space. They were discovered by Cantor and co-workers in the late 1970s/early 1980s, but have not been studied intensively until the last decade or so. This review describes: the extensive range and complexity of multicomponent phase space, including the prevalence of single (or relatively few) phases and the paucity of intrinsically new multicomponent compounds; the thermodynamics of multicomponent single-phase materials such as the Cantor alloys, and the extent to which they are stabilised by a high configurational entropy; the multiplicity and complexity of local atomic configurations and associated lattice strains in multicomponent single-phase high-entropy materials such as the Cantor alloys; the effect of multiple atomic configurations and lattice strains on the rate of atomic diffusion and on the creation and motion of dislocations; and the resulting excellent mechanical properties, equal to and sometimes exceeding the very best high strength steels, nickel superalloys and hard ceramics, with enormous potential for future further enhancement and optimisation.
Abstract
The CoCrFeNiMn multicomponent is one of the most widely and best studied of all high-entropy alloys (HEAs) since its exceptional properties suggest potential uses as a structural material in many industrial applications. In practice, a good balance between strength and ductility is one of the most important challenges in developing alloys in modern materials science and engineering. There have been many attempts to overcome the strength-ductility trade-off in the CoCrFeNiMn alloy due to its relatively low strength. These attempts include adding a minor sixth element, such as oxide or carbide particles, and also developing thermomechanical processing for grain refinement or precipitation to produce a tailored microstructure with optimum mechanical properties. This review describes the deformation mechanisms and the microstructural evolutions in this alloy during plastic deformation under different conditions of temperature, strain and strain rate where these are important for the processing and manufacturing of the alloy. In addition, this study provides a perspective on the behavior of the alloy under high temperature exposure and also under cyclic loading which is generally the most important factor in industrial applications. This understanding demonstrates that there is a very large potential for the future enhancement and optimization of this and other comparable HEAs.