Influence of cooling rate on the microstructure and room temperature mechanical properties in the refractory AlMo0.5NbTa0.5TiZr superalloy
Source: BAM
Compositionally complex alloys (CCAs) are a class of materials that offer unique microstructures and properties due to their complex composition. They have gained attention as potential alternatives to conventional alloys that face limitations in fulfilling high-temperature material requirements. The AlMo0.5NbTa0.5TiZr CCA, is composed mainly of a dual-phase A2/B2 microstructure similar to the γ/γ' microstructure observed in well-known Ni-based superalloys. This microstructure and its high compression properties at room and high temperatures make the alloy a promising candidate for high-temperature structural applications.
However, the ductility of this alloy and other similar alloys is a concern. Previous studies have attempted to improve the room-temperature ductility of CCAs through phase inversion and compositional adjustments. Yet, while the ductility increases, the strength decreases. Therefore, this study aims to explore the influence of cooling rate after solution treatment on the microstructure and room temperature mechanical properties of the AlMo0.5NbTa0.5TiZr alloy in order to assess potential alternatives for enhancing ductility.
The microstructure analysis reveals that a faster cooling rate formed a finer and more homogeneous A2/B2 nanostructure and suppressed an Al-Zr-rich intermetallic along the grain boundaries. The lattice misfit between the A2 and B2 phases decreased with increasing cooling rates. It is proposed that the complex coarsening behavior of the A2/B2 microstructure is strongly influenced by the lattice misfit between the phases.
However, it is noteworthy that the fracture toughness (Kc = 4.2 ± 0.4 MPa∙m1/2) remained unaffected by the cooling rate, indicating the absence of brittleness reduction, whereas the increase in nanohardness is attributed to the decrease in A2 precipitate size with an increasing cooling rate. Finally, the study highlights the relationship between cooling rate, microstructure, and room temperature mechanical properties in the AlMo0.5NbTa0.5TiZr CCA. The findings provide insights into the design and optimization of refractory high-entropy alloys for structural applications.
Influence of cooling rate on the microstructure and room temperature mechanical properties in the refractory AlMo0.5NbTa0.5TiZr superalloy
Patricia Suárez Ocaño, Anna Manzoni, I. Lopez-Galilea, B. Ruttert, G. Laplanche, Leonardo Agudo Jácome
Published in Journal of Alloys and Compounds, 2023, Volume 949, Page 169871 et sqq.
BAM Materials Engineering
BAM Materialography, Fractography and Ageing of Engineered Materials