Microstructure evolution and mechanical properties of cold rolling 18Ni300 maraging steel produced by twin-roll strip casting

In this study, the microstructure evolution and strengthening behavior of a maraging steel subjected to cold rolling following sub-rapid solidification are investigated, with the conventional solution treatment being omitted. The results show that sub-rapid solidification produces an as-cast strip with a supersaturated martensitic matrix, providing a high chemical driving force for subsequent precipitation, while short-time high-temperature holding before hot rolling effectively reduces the millimeter-scale microsegregation inherited from solidification. A low-reduction cold-rolling step is subsequently introduced. In the absence of solution treatment, the cold-rolling-induced dislocations are retained prior to aging and act as heterogeneous nucleation sites and fast diffusion pathways, thereby markedly accelerating the precipitation kinetics of nanoscale precipitates during aging. Consequently, effective precipitation strengthening is achieved within a short aging time. After aging at 480 °C for 0.5 h, the maraging steel achieves an ultimate tensile strength of ~1.7 GPa with an elongation of ~11%. Prolonged aging further increases the ultimate tensile strength to ~2.1 GPa owing to the increased volume fraction of precipitates, accompanied by a decrease in elongation to ~6.6%. These results demonstrate that retaining cold-rolling-induced dislocations by omitting solution treatment can effectively enhance the aging response of maraging steel following sub-rapid solidification, providing a potential strategy for simplifying its conventional processing route while maintaining a favorable strength–ductility balance.