In the present study, 3D atom probe was used to study the effect of increased Mo (1–3 wt%) on clustering in secondary hardening ultra-high strength steels. Clusters have been classified into three categories, namely, Type I, Type II, and Type III with the (Cr + Mo)/C ratio of <1.5, 1.5–3.25, and >3.25, respectively. Cluster evolution suggests that size and volume fraction (Vf) of Type II clusters increase continuously from as-quenched to aged samples, while the number density (Nv) increases in 400 °C aged sample and decreases in 450 and 500 °C samples. On the other hand, Nv and Vf of both Type I and Type III clusters decrease on aging. This work clearly suggests that on aging, Type II clusters, which are close to M2C stoichiometry, become most stable, which may eventually either become M2C precipitates upon prolonged aging or act as potential nuclei for the precipitation of equilibrium M2C precipitates.

在本研究中，使用3D原子探针研究了增加的Mo（1-3 wt％）对二次淬火超高强度钢中聚集的影响。簇已即，分为三类，I型，II型，和III型分别与（CR + Mo）的/的C比<1.5，1.5-3.25，和> 3.25。团簇演化表明，II型团簇的大小和体积分数（V f）从淬火到老化样品均不断增加，而数密度（N v）在400°C老化样品中增加，而在450和500°C样品中减少。另一方面，N v和V f两者的I型和III型集群减少老化。这项工作清楚地表明，在老化过程中，接近M 2 C化学计量的II型团簇变得最稳定，随着时间的延长，II型团簇最终可能会变成M 2 C沉淀，或者可能成为平衡M 2 C沉淀的潜在核。沉淀。