The influence of Fe variations on the phase stability of CrMnFexCoNi alloys following long-duration exposures at intermediate temperatures

The equiatomic CrMnFeCoNi alloy exhibits many desirable properties, but its susceptibility to the formation of embrittling intermetallic phases, makes it unsuitable for structural applications at elevated temperatures. As a result, there has been increasing interest in developing alternative alloys...

Full description

Saved in:
Bibliographic Details
Published in:Intermetallics 2021-04, Vol.131, p.107108, Article 107108
Main Authors: Bloomfield, M.E., Christofidou, K.A., Monni, F., Yang, Q., Hang, M., Jones, N.G.
Format: Article
Language:English
Subjects:
Alloys
Chemical precipitation
Depletion
Electron microscopy
Ferrous alloys
Grain boundaries
Heat treating
Heat treatment
High temperature
High-entropy alloys
Intermetallic phases
Microstructure
Phase stability
Precipitates
Prediction
Sigma phase precipitation
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The equiatomic CrMnFeCoNi alloy exhibits many desirable properties, but its susceptibility to the formation of embrittling intermetallic phases, makes it unsuitable for structural applications at elevated temperatures. As a result, there has been increasing interest in developing alternative alloys from the CrMnFeCoNi system that avoid this limitation. Here we present a detailed study of phase stability in a CrMnFexCoNi series of alloys, where x = 0, 0.5, 1.5 (in atomic ratio), following long-duration heat treatments of 1000 h at 900 and 700 °C, and up to 5000 h at 500 °C. Each alloy was single phase fcc following homogenisation. After exposure at 900 °C, large σ phase precipitates were present in the CrMnCoNi alloy, but alloys containing ≥0.5 Fe remained single phase fcc. At 700 °C, the alloys investigated all contained the σ phase. Cr-bcc precipitates were also present in the CrMnCoNi and CrMnFe0.5CoNi alloys and Cr carbide precipitates featured in the CrMnFe1.5CoNi alloy. Heat-treatment of the CrMnCoNi alloy at 500 °C caused a partial bulk decomposition of the fcc matrix, which produced a fine-scale intergrowth of phases: σ, NiMn-L10, Cr-bcc and a secondary solute-depleted fcc phase. In the alloy containing 0.5 Fe, cellular regions consisting of a NiMn-L10, Cr-bcc and solute-depleted matrix phase, developed along the grain boundaries. NiMn-L10 and Cr-rich precipitates also formed on grain boundaries in the 1.5 Fe alloy. From these experimental observations, it was clearly established that Fe stabilises the fcc matrix relative to the σ and bcc phases. [Display omitted] •Fe stabilised the fcc matrix relative to the σ and bcc phases.•At 500 °C heat-treatments of 5000 h were required to identify precipitate phases.•TCHEA3 failed to predict the formation of NiMn-L10 and FeCo–B2 phases at 500 °C.
ISSN:0966-9795
1879-0216
DOI:10.1016/j.intermet.2021.107108