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

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. •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.