Phase Equilibria in the Nb-Rich Region of Al-Nb-Sn at 900 and 1200 °C

Ioannis Papadimitriou; Claire Utton; Panos Tsakiropoulos

doi:10.3390/ma12172759

Phase Equilibria in the Nb-Rich Region of Al-Nb-Sn at 900 and 1200 °C

Materials (Basel). 2019 Aug 28;12(17):2759. doi: 10.3390/ma12172759.

Authors

Ioannis Papadimitriou¹, Claire Utton², Panos Tsakiropoulos¹

Affiliations

¹ Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, England, UK.
² Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, England, UK. c.utton@sheffield.ac.uk.

Abstract

The Al-Nb-Sn phase diagram was studied experimentally in the Nb-rich region to provide important phase equilibria information for alloy design of Nb-silicide based materials for aero engine applications. Three alloys were produced: Nb-17Al-17Sn, Nb-33Al-13Sn and Nb-16Al-20Sn (at.%). As-cast and heat-treated alloys (900 and 1200 °C) were analysed using XRD (X-ray diffraction) and SEM/EDS (scanning electron microscopy/ electron dispersive x-ray spectroscopy). Tin showed a high solubility in Nb₂Al, reaching up to 21 at.% in the Sn-rich areas, substituting for Al atoms. Tin and Al also substituted for each other in the A15 phases (Nb₃Al and Nb₃Sn). Tin showed limited solubility in NbAl₃, not exceeding 3.6 at.% as it substituted Al atoms. The solubility of Al in NbSn₂ varied from 4.8 to 6.8 at.%. A ternary phase, Nb₅Sn₂Al with the tI32 W₅Si₃ crystal structure, was found to be stable. This phase was observed in the 900 °C heat-treated samples, but not in the 1200 °C heated samples.

Keywords: Nb5Sn2Al; aluminium; engineering and physical sciences research council (EPSRC)-rolls royce (RR) strategic partnership; niobium; phase equilibria; tin.

Grants and funding

EP/H500405/1, EP/L026678/1/Engineering and Physical Sciences Research Council