Synergistic alloying effects on nanoscale precipitation and mechanical properties of ultrahigh-strength steels strengthened by Ni3Ti, Mo-enriched, and Cr-rich co-precipitates

The synergistic effects of Mo, Ti, and Cr on nanoscale precipitation mechanical properties maraging stainless steels were systematically studied using high-resolution scanning transmission electron microscopy, atom probe tomography (APT), thermodynamic first-principles calculations, tests. Our results reveal a notable pathway involving the co-precipitation Ni3Ti, Mo-enriched, Cr-rich precipitates; their formations are not separated, but rather highly interacted. APT indicate that Mo partitions to Ni3Ti precipitate core in early stage precipitation, which doubles number density precipitates. calculations partitioning only increases chemical driving force, also reduces strain energy for nucleation, thereby accelerating precipitation. As proceeds, atoms rejected from interface between precipitates matrix, leads heterogeneous nucleation Mo-enriched outer surface This substantial size refinement In addition, formation consumes Ni substantially inhibits spinodal decomposition refines cooperative strengthening co-precipitates development new with strength 1.8 GPa; contributions these quantitatively evaluated terms shearing Orowan dislocation looping mechanisms.