Atom probe field-ion microscopy study of ageing behaviour of a model FeNiCoMo maraging steel

Abstract

This paper reports an atom probe field-ion microscopy (APFIM) study of the ageing reactions in a model Fe18.2%Ni8.8%Co2.9% Mo (at. %) maraging steel, using both the conventional APFIM and the position-sensitive atom probe (POSAP). Two different families of intermetallic phases (ω-phase and Fe 7Mo 6) have been found to contribute to age-hardening. The composition and morphology of these precipitates were studied in the alloy aged at 414°C and 510°C. No evidence was found for the existence of Mo-rich clusters in the as-quenched alloy. The APFIM results are compared with studies by Servant et al. using other techniques, and previous studies on a commercial Ti-containing steel by the authors.