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Microstructural Degradation of the AlMo 0.5 NbTa 0.5 TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures

Published version
Peer-reviewed

Change log

Authors

Whitfield, Tamsin E.  ORCID logo  https://orcid.org/0000-0002-6456-4820
Jones, C. Neil 

Abstract

Refractory metal high-entropy superalloys (RSA), which possess a nanoscale microstructure of B2 and bcc phases, have been developed to offer high temperature capabilities beyond conventional Ni-based alloys. Despite showing a number of excellent attributes, to date there has been little consideration of their microstructural stability, which is an essential feature of any material employed in high temperature service. Here, the stability of the exemplar RSA AlMo0.5NbTa0.5TiZr is studied following 1000 h exposures at 1200, 1000 and 800 °C. Crucially, the initial nanoscale cuboidal B2 + bcc microstructure was found to be unstable following the thermal exposures. Extensive intragranular precipitation of a hexagonal Al-Zr-rich intermetallic occurred at all temperatures and, where present, the bcc and B2 phases had coarsened and changed morphology. This microstructural evolution will concomitantly change both the mechanical and environmental properties and is likely to be detrimental to the in-service performance of the alloy.

Description

Keywords

refractory metal high entropy alloys, phase transformation/precipitation, intermetallics, thermodynamics

Journal Title

Entropy

Conference Name

Journal ISSN

1099-4300

Volume Title

23

Publisher

MDPI
Sponsorship
Engineering and Physical Sciences Research Council (EP/M005607/1)
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