Low-temperature embrittlement in Fe–Cr–X (X = Ni, Al, Co, etc.) alloys governed by thermodynamics, kinetics and mechanics: a review

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Abstract
The low-temperature embrittlement limits the service temperature of ferritic and duplex stainless steels. The effects of alloying elements added to Fe–Cr binary system on the low-temperature embrittlement have been reviewed critically. Prior literature on the underlying phase transformation, i.e . , phase separation (PS) and changes of mechanical properties, is surveyed. The available literature indicates that the rate of PS is accelerated by Ni or Co in Fe–Cr binary system. The increased kinetics of PS also lead to an enhanced hardening rate during aging for Ni and Co alloyed Fe–Cr alloys. In low Cr (< 17 wt.%) ferritic alloys, the additions of Al or Co can reduce embrittlement because these elements contribute to lowering the driving force for PS. The influence of other alloying elements such as Mo, Cu, Mn, Nb, and Ti is inconclusive but also discussed here. Thermodynamic and kinetic calculations were performed to evaluate current CALPHAD databases and to further investigate the thermodynamic and kinetic reasons for the effect of the additional alloying elements added to Fe–Cr alloy on PS. Some indications were provided for improving physically-based predictions of low-temperature embrittlement as well as opportunities to mitigate the phenomenon by alloying.
Funding Information
  • China Scholarship Council (201700260207)
  • Jernkontoret
  • EIT RawMaterials (18317)
  • Royal Institute of Technology

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