In Situ Observations of the Microstructural Evolution during Heat Treatment of a PH 13‐8 Mo Maraging Steel

The standard heat treatment of PH 13-8 Mo maraging steels consists solution annealing and subsequent aging. Herein, it is investigated how an additional intercritical step prior to aging affects the microstructure, and, consequently, mechanical properties a steel. In situ techniques by means high-temperature electron backscatter diffraction X-ray are applied study microstructural changes during addition, high-resolution investigation methods, such as transmission microscopy atom probe tomography supplemented Kikuchi diffraction, used for in-depth characterization microstructure. results reveal that diffusion-controlled martensite austenite transformation accompanied partitioning substitutional atoms Cr, Ni, takes place annealing. As result annealing, inhomogeneous distribution Ni remains in microstructure after martensitic transformation. Consequently, formation reverted facilitated due existing Ni-enriched zones martensite. Since fracture toughness significantly enhanced compared treatment, suggested this improvement related increased phase fraction austenite.