Accelerated precipitation in the AFA stainless steel Fe–20Cr–30Ni–2Nb–5Al via cold working

• This alloy forms B2 NiAl and C14 Fe2Nb precipitates after aging up to 240 h at 800 °C.
• After cold work, at 700 °C γ′-Ni3Al precipitates form along with B2 and C14 phase.
• Cold work at 700 °C and 800 °C increased the precipitation kinetics of the alloy.
• Aging temperature and cold work had a distinct influence on the material hardness.
• With sufficient cold work, a finer dispersion of matrix particles could be attained.

The effects of cold work on the microstructural evolution during aging of a solutionized alumina-forming austenitic stainless steel, Fe–20Cr–30Ni–2Nb–5Al (at.%), were investigated using scanning electron microscopy, transmission electron microscopy, and scanning transmission electron microscopy. Cold work prior to aging at either 700 °C or 800 °C facilitated the heterogeneous precipitation of both Laves phase and B2-type NiAl precipitates. While often co-located after cold work, these particles were distinct. γ′-Ni3Al precipitates were also observed in samples aged at 700 °C with 90% prior cold work. Compared to material that had not been strained, defects introduced by 50 and 90% cold work at 700 °C and 90% cold work at 800 °C not only caused a more rapid precipitation in the matrix but also an increase in the total volume fraction of precipitates as compared to material that had been simply aged.