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 conduct together with Dr. Sandlöbes at RWTH Aachen and the department of Prof. Neugebauer ab initio calculations for designing new Mg – Li alloys. Ab initio calculations can accurately predict basic structural, mechanical, and functional properties using only the atomic composition as a basis.
The wide tunability of the fundamental electronic bandgap by size control is a key attribute of semiconductor nanocrystals, enabling applications spanning from biomedical imaging to optoelectronic devices. At finite temperature, exciton-phonon interactions are shown to exhibit a strong impact on this fundamental property.
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…
In this project we study - together with the department of Prof. Neugebauer and Dr. Sandlöbes at RWTH Aachen - the underlying mechanisms that are responsible for the improved room-temperature ductility in Mg–Y alloys compared to pure Mg.
Efficient harvesting of sunlight and (photo-)electrochemical conversion into solar fuels is an emerging energy technology with enormous promise. Such emerging technologies depend critically on materials systems, in which the integration of dissimilar components and the internal interfaces that arise between them determine the functionality.
In this project, we work on the use of a combinatorial experimental approach to design advanced multicomponent multi-functional alloys with rapid alloy prototyping. We use rapid alloy prototyping to investigate five multicomponent Invar alloys with 5 at.% addition of Al, Cr, Cu, Mn and Si to a super Invar alloy (Fe63Ni32Co5; at.%), respectively…
A wide range of steels is nowadays used in Additive Manufacturing (AM). The different matrix microstructure components and phases such as austenite, ferrite, and martensite as well as the various precipitation phases such as intermetallic precipitates and carbides generally equip steels with a huge variability in microstructure and properties.
Laser Powder Bed Fusion (LPBF) is the most commonly used Additive Manufacturing processes. One of its biggest advantages it offers is to exploit its inherent specific process characteristics, namely the decoupling the solidification rate from the parts´volume, for novel materials with superior physical and mechanical properties. One prominet…
We have studied a nanocrystalline AlCrCuFeNiZn high-entropy alloy synthesized by ball milling followed by hot compaction at 600°C for 15 min at 650 MPa. X-ray diffraction reveals that the mechanically alloyed powder consists of a solid-solution body-centered cubic (bcc) matrix containing 12 vol.% face-centered cubic (fcc) phase. After hot compaction, it consists of 60 vol.% bcc and 40 vol.% fcc. Composition analysis by atom probe tomography shows that the material is not a homogeneous fcc–bcc solid solution
Magnetic properties of magnetocaloric materials is of utmost importance for their functional applications. In this project, we study the magnetic properties of different materials with the final goal to discover new magnetocaloric materials more suited for practical applications.
Electro-responsive interfaces alter their properties in response to an electric potential trigger. Hence, such 'smart' interfaces offer exciting possibilities for applications in, for instance, microfluidics, separation systems, biosensors and -analytics.
