In this project, we work on a generic solution to design advanced high-entropy alloys (HEAs) with enhanced magnetic properties. By overturning the concept of stabilizing solid solutions in HEAs, we propose to render the massive solid solutions metastable and trigger spinodal decomposition. The motivation for starting from the HEA for this approach is to provide the chemical degrees of freedom required to tailor spinodal behaviour using multiple components.
Since its first emergence in 2004, the HEA concept has aimed at stabilizing single- or dual-phase multi-element solid solutions through high mixing entropy. Here, we change this strategy and render such massive solid solutions metastable, to trigger spinodal decomposition for improving the alloys’ magnetic properties. The motivation for starting from a HEA for this approach is to provide the chemical degrees of freedom required to tailor spinodal behavior using multiple components. The key idea is to form Fe-Co enriched regions which have an expanded volume (relative to unconstrained Fe-Co), due to coherency constraints imposed by the surrounding HEA matrix. As demonstrated by theory and experiments, this leads to improved magnetic properties of the decomposed alloy relative to the original solid solution matrix. In a prototype magnetic FeCoNiMnCu HEA, we show that the modulated structures, achieved by spinodal decomposition, lead to an increase of the Curie temperature by 48% and a simultaneous increase of magnetization by 70% at ambient temperature as compared to the homogenized single-phase reference alloy.
In this project nanoprecipitates are designed via elastic misfit stabilization in Fe–Mn maraging steels by combining transmission electron microscopy (TEM) correlated atom probe tomography (APT) with ab initio simulations. Guided by these predictions, the Al content of the alloys is systematically varied...
Interstitial alloying can improve the mechanical properties of high-entropy alloys (HEAs). In some cases, the interstitial-alloying impact is very different from those in conventional alloys. We investigate the effect of interstitial alloying in fcc CrMnFeCoNi HEA as well as bcc refractory HEAs, particularly focusing on the solution energies and…
The structure of solvent at solid-liquid interfaces influences the interactions and reactions occurring on it, which has strong impacts for applications in diverse fields, such as wetting phenomena, electrochemistry or biotechnology. We particularly try to understand the influence of nanoscale structures formed on functional interfaces on the…
Future technology challenges will no longer be simply addressed by today's materials and processing solutions, which are often based on trial and error. Instead, guidance will be attained from correlative experimental and theoretical research bridging all length scales.
Within the EU project „ADVANCE - Sophisticated experiments and optimisation to advance an existing CALPHAD database for next generation TiAl alloys”, MPIE collaborated with Thermocalc-Software AB, Stockholm, Montanuniversität Leoben and Helmholtz-Zentrum Hereon, Geesthacht. At MPIE the focus lay on the production and heat treatments of model alloys…
The promising mechanical properties of metallic glasses (MG) such as high hardness, yield strength, and toughness [1] are desirable to exploit for structural applications. Monolithic MGs lack grains and grain boundaries; thus, the mechanical properties of MGs are depending on the chemistry as well as processing and testing conditions. However…