Struktur und thermodynamische Eigenschaften einer TiZrNbHfTa Hochentropielegierung
Mechanische Eigenschaften von metallischen Werkstoffen und ihre mikrostrukturellen Ursachen
Zusammenfassung der Projektergebnisse
The following bullet points summarize the most important scientific and non-scientific aspects of the project: The equiatomic fcc-FeNiCoCrMn, bcc-TiNbHfTaZr HEAs and their sub-alloys with less chemical complexity were prepared by arc-melting, cold-crucible casting and thermomechanical treatment in order to investigate phase stability, lattice strain and solid solution hardening behaviour. - The sub-alloys consisting of less number of constituent elements (fcc: equiatomic FeNiCoCr, FeNiCo, FeNi alloys and pure Ni / bcc: equiatomic TiNbHfTa, TiNbHf, TiNb alloys and pure Nb) were selected to be investigated in a comparison with the HEAs. - Quantitative determination of the structure formation especially with respect to the lattice distortion and the local atomic distribution in the bcc/fcc crystal lattice in both bulk and atomic scale was derived by performing (high-energy) x-ray diffraction study with the atomic pair distribution function (PDF) method and the Bragg peak broadening analysis. - All studied alloy samples formed single fcc or bcc solid solution phase and the thermal analysis revealed their thermal stability between 300 - 1500 K. - The micro lattice strain in the HEAs and their sub-alloys was quantified by Williamson-Hall methods on the Bragg intensities. The levels of micro lattice strain were not significantly different among the samples having different number of constituent elements. - To assess the lattice distortion present in the TiZrNbHfTa HEA, the local lattice strain has been studied through X-ray total scattering measurements, in comparison with four single phase bcc materials, with varying compositional complexity (Pure Nb, TiNb, TiNbHf and TiNbHfTa). - Significant PDF peak broadening was observed from multi component alloys ( n ≥ 3) indicating largely displaced atoms from their ideal lattice positions. - The TiZrNbHfTa and FeNiCoCrMn HEAs exhibited the broadest PDF peak, suggesting the highest level of local lattice strain. - PDF peak broadening and tensile yield strength did not exhibited a linear relationship with number of constituent n (compositional complexity and configurational entropy ΔSconf.). - The PDF peak width and yield strength appears to vary linearly with atom size misfit δr. - The lattice of fcc FeNiCoCrMn HEA is not anomalously distorted compared to an average fcc structure. - The evidence from this study suggests that the atomic size misfit is more important factor than the number of constituent elements in the determination of lattice distortion.
Projektbezogene Publikationen (Auswahl)
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Microstructure, mechanical and thermal oxidation behavior of AlNbTiZr high entropy alloy, Intermetallics 100, 9 (2018)
Jayaraj, J.; Thirathipviwat, Pramote; Han, Junhee & Gebert, Annett
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A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy, Journal of Alloys and Compound 790, 266 (2019)
Thirathipviwat, P.; Song, G.; Jayaraj, J.; Bednarcik, J.; Wendrock, H.; Gemming, T.; Freudenberger, J.; Nielsch, K. & Han, J.
