Within the EU project „ADVANCE - Sophisticated experiments and optimisation to advance an existing CALPHAD database for next generation TiAl alloys” MPIE is collaborating with Thermocalc-Software AB, Stockholm, Montanuniversität Leoben and Helmholtz-Zentrum Geesthacht. At MPIE the focus lies on the production and heat treatments of model alloys. By analysing them through metallography, X-ray diffraction, electron probe microanalysis and differential thermal analysis, the necessary data are obtained. Colleagues in Leoben perform atom probe tomography and transmission electron microscopy and in Geesthacht in situ synchrotron X-ray diffraction is carried out. All obtained data are optimised at the company Thermocalc and checked for consistency before they are implemented into the database.
Alloys based on the intermetallic phase γ-TiAl constitute a new class of materials. They have high specific strength and are therefore specifically suited for applications where the weight of moving parts has to be considered, e.g. compressor blades in aero engines or turbo chargers for vehicles. Compared to established Ni- and Co-base superalloys, γ-TiAl alloys are lighter and therefore more energy efficient.
Todays alloy developments crucially depend on data-based CALPHAD programs. CALPHAD is an acronym for calculation of phase diagrams. The databases contain specific thermodynamic values for phase equilibria and phase transformations, and compositions of the phases in dependence on temperature and composition of an alloy. The databases allow to calculate which phases are stable at certain temperatures, their volume fractions and compositions within regions, where no experimental results are available. This enables prediction of the microstructures and, from this, conclusions about expected mechanical properties. Thereby, employment of these databases enables a time-efficient development of novel materials.
Example of an aligned microstructure of a Ti-Al-Nb alloy.
Kahrobaee, Z.; Palm, M.: Determination of phase equilibria in the Ti–Al–Si system at 800–1200 °C. In: Proceedings Intermetallics 2021, pp. 78 - 79. Intermetallics 2021, Bad Staffelstein, Germany, October 04, 2021 - October 08, 2021. (2021)
Distl, B.; Dehm, G.; Stein, F.: Effect of Oxygen on High‐temperature Phase Equilibria in Ternary Ti‐Al‐Nb Alloys. Zeitschrift für anorganische und allgemeine Chemie 646 (14), pp. 1151 - 1156 (2020)
Distl, B.; Palm, M.; Stein, F.; Rackel, M. W.; Hauschildt, K.; Pyczak, F.: Phase equilibria investigations in the ternary Ti–Al–Nb system at elevated temperatures. Intermetallics 2019, Bad Staffelstein, Germany (2019)
Kahrobaee, Z.; Stein, F.; Palm, M.: Experimental evaluation of the isothermal section of the Ti–Al–Zr ternary system at 1273 K. In: Proceedings Intermetallics, pp. 174 - 175. Intermetallics 2019, Bad Staffelstein, Germany, September 30, 2019 - October 04, 2019. (2019)
In this project we pursue recent developments in the field of austenitic steels with up to 18% reduced mass density. The alloys are based on the Fe-Mn-Al-C system.
Local lattice distortion is one of the core effects in complex concentrated alloys (CCAs). It has been expected that the strength CCAs can be improved by inducing larger local lattice distortions. In collaboration with experimentalists, we demonstrated that VCoNi has larger local lattice distortions and indeed has much better strength than the…
Water electrolysis has the potential to become the major technology for the production of the high amount of green hydrogen that is necessary for its widespread application in a decarbonized economy. The bottleneck of this electrochemical reaction is the anodic partial reaction, the oxygen evolution reaction (OER), which is sluggish and hence…
In order to explore the possibility of using high entropy alloys (HEAs) for functional applications such as magnetic refrigeration it is necessary to have an in-depth understanding of their magnetic properties. The main goal of this project is to understand and improve the magnetic properties (e.g., saturation magnetization, Curie temperature etc.) in different medium and HEAs.
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…
In this project we study a new strategy for the theory-guided bottom up design of beta-Ti alloys for biomedical applications using a quantum mechanical approach in conjunction with experiments. Parameter-free density functional theory calculations are used to provide theoretical guidance in selecting and optimizing Ti-based alloys...
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 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…
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...
Wear-related energy loss and component damage, including friction and remanufacturing of components that failed by surface contacts, has an incredible cost. While high-strength materials generally have low wear rates, homogeneous deformation behaviour and the accommodation of plastic strain without cracking or localised brittle fracture are also…
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.
