Characterization of nanoscale NiAl-type precipitates in a ferritic steel by electron microscopy and atom probe tomography

The microstructure of NiAl-type (β′) precipitates in an aged ferritic steel (Fe–12.7Al–9Ni–10.2Cr–1.9Mo, at.%) is characterized by transmission and analytical electron microscopy (AEM) and atom probe tomography (APT). The alloy shows a duplex precipitation of β′ particles: primary with an average diameter of 130 nm and secondary with an average diameter of 3 nm. Based on APT, the primary and secondary β′ have compositions of Ni41.2Al43.6Fe12.7Cr0.8Mo1.4 and Ni26.3Al41.6Fe26.9Cr3.3Mo1.7, respectively.