A high-strength precipitation hardened cobalt-free high-entropy alloy
Matthew Luebbe, Jiaqi Duan, Fan Zhang, Jonathan Poplawsky, Hans Pommeranke, Maalavan Arivu, Andrew Hoffman, Haiming Wen
Recent studies on precipitation-hardened high-entropy alloys (HEAs) demonstrate their high strength and thermal stability, making them promising materials for high-temperature structural applications such as nuclear reactors. However, many existing HEAs contain cobalt (Co), which is unsuitable for nuclear applications because of the long-term activation issue of Co. Co is also expensive and considered a critical material for other applications. Therefore, it is desired to exclude Co from the composition. A Co-free (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8 HEA was developed and studied in this work. In contrast to previous Co-free HEAs, this alloy is close to equiatomic in its composition and promises a more pronounced high-entropy effect. Scanning electron microscopy, transmission electron microscopy, atom probe tomography, and synchrotron-based, high-energy X-ray diffraction were used to characterize this alloy and revealed a complex four-phase structure with an FCC matrix, γ′ precipitates, and a network of B2 and χ phase particles. This structure granted 2151 MPa compressive strength and good thermal stability, but with limited ductility and slow precipitation kinetics. A strengthening analysis of the alloy shows that the small γ′ precipitates provided the most significant strengthening contribution (1244 GPa). The strengthening effect from the B2 and χ networks is also considerable, adding 312 MPa and 788 MPa for B2 and χ, respectively. This study lays the foundation for the continued development of high-strength Co-free HEAs with improved and satisfactory ductility.
, Duan, J.
, Zhang, F.
, Poplawsky, J.
, Pommeranke, H.
, Arivu, M.
, Hoffman, A.
and Wen, H.
A high-strength precipitation hardened cobalt-free high-entropy alloy, Materials Science and Engineering A, [online], https://doi.org/10.1016/j.msea.2023.144848, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935813
(Accessed December 8, 2023)