Huang C.-YYen H.-W.HUNG-WEI YEN2021-08-052021-08-05202110445803https://www.scopus.com/inward/record.uri?eid=2-s2.0-85107057845&doi=10.1016%2fj.matchar.2021.111216&partnerID=40&md5=daeff29861362780418244ac53a3197ehttps://scholars.lib.ntu.edu.tw/handle/123456789/576921In this work, nano precipitates in stainless maraging steel (Custom 475) were investigated using high-resolution transmission electron microscopy. In this steel, aging induces three transformation products, NiAl-B2 phase, R phase and austenite, which contribute various hardening effects dependent on the aging temperature. In the steel aged at 480 °C, precipitation of NiAl-B2 phase was the primary reaction and led to slow incremental hardening. No hardening effect was observed in the steel aged at 650 °C despite the presence of austenite of over 25 vol% and coarse B2 and R phases. Efficient hardening was obtained by aging at 520 °C, and the maximum hardness (601 HV) was achieved when the steel was aged for 4 h. This high strength is attributed to the formation of both B2 and R nano precipitates. Moreover, lattice images and diffractograms clarified the crystal structure of the R phase and its orientation relationship with the martensite matrix. This work provides comprehensive insights into precipitation behaviors in Custom 475 maraging steel. ? 2021 Elsevier Inc.journal article10.1016/j.matchar.2021.1112162-s2.0-85107057845