Refractory Alloys
Refractory alloys are based on metals with very high melting points, such as W, Ta, Nb, Mo and V, and are used in nuclear, fusion and aerospace environments for their strength at high temperature. Refractory multi-principal element (high-entropy) alloys combine several of these elements in solid solution, but many, especially tungsten-rich ones, are brittle at room temperature, which makes forming, machining and additive manufacturing difficult. Much computational work therefore seeks electronic or elastic descriptors that predict which compositions remain ductile.
Designing printable W–Ta–Nb alloys (2026)
Abdelmaqsoud and coworkers combined machine-learned potential and DFT elastic constants with CALPHAD solidus temperatures to choose W–Ta–Nb compositions that balance ductility and melting point, settling on about 10 at.% Nb. Six alloys from 20 to 80 at.% W, printed by powder-blown directed energy deposition, showed lack of fusion and unmelted W and Ta particles in lower layers, and intergranular microcracking that increased with W content in line with the inverse Pugh ratio C’/K. The nominal W20Ta70Nb10 and W30Ta60Nb10 alloys showed no visible intergranular cracking and were proposed for further mechanical testing (Abdelmaqsoud et al. 2026). Summary: abdelmaqsoud2026.
The valley of brittleness in Ta-W and other group V-VI binaries (2026)
Using a rigid band model built on the DOS of equiatomic B2 TaW, Abdelmaqsoud, Kitchin and Widom linked the transition from ductile Ta-rich to brittle W-rich Ta-W alloys to the Fermi level moving from a high, T2g-dominated shoulder (VEC 5.0 to 5.5) into a pseudogap (VEC 5.5 to 6.0). The rigid band model held well across Ta-W compositions and structures, including a special quasirandom structure and the ground-state ordering. Pugh ratios of VCr, NbMo, NbW and TaMo also peak below x = 1/2 and fall at higher group VI content, with quantitative differences between systems. Energy-minimizing (noncubic) orderings have lower Pugh ratios than the cubic cells, suggesting chemical short-range order reduces ductility (Abdelmaqsoud et al. 2026). Summary: abdelmaqsoud2026a.