Abstract
In support of computational design of coherent aluminide strengthened Nb alloys, the phase equilibria in a series of six Nb-Pd-Hf-Al alloys were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD). All alloys were heat treated at 1200°C for 200 h, while three alloys were also heat treated at 1500°C for 200 h. Three-phase equilibria and two-phase equilibria were observed in two alloys at both temperatures. Two more alloys also exhibited three-phase equilibria at 1200 °C, while one alloy exhibited two-phase equilibria at 1200 °C. A final alloy revealed four-phase equilibria at both temperatures, confirming the presence of a unique tie-tetrahedron in the Nb-Pd-Hf-Al system. Based on the characterization of phases by SEM and XRD, the Nb-Pd-Hf-Al partial phase diagram at 1200 °C has been constructed. Such phase diagrams provide the basis for designing precipitation-strengthened Nb-based superalloys.
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Misra, A., Ghosh, G. & Olson, G.B. Phase relations in the Nb-Pd-Hf-Al system. J Phs Eqil and Diff 25, 507–514 (2004). https://doi.org/10.1007/s11669-004-0063-3
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DOI: https://doi.org/10.1007/s11669-004-0063-3