The influence of aging temperature on microstructure and mechanical properties of Cr15Ni5 precipitation hardening stainless steel (15-5 PH stainless steel) were investigated at aging temperature range of 440–610 °C. The tensile properties at ambient temperature of the 15-5 PH stainless steel processed by different aging temperatures were tested, and the microstructural features were further analyzed utilizing optical microscope (OM), transmission electron microscope (TEM), electron backscatter diffraction (EBSD) as well as X-ray diffraction (XRD), respectively. Results indicated the strength of the 15-5 PH stainless steel was firstly decreased with increment of aging temperature from 440 to 540 °C, and then increased with the increment of aging temperature from 540 to 610 °C. The strength and ductility were well matched at aging temperature 470 °C, and the yield strength, tensile strength as well as elongation were determined to be 1170 MPa, 1240 MPa and 24%, respectively. The microstructures concerning to different aging temperatures were overall confirmed to be lath martensite. The strengthening mechanisms induced by dislocation density and the second phase precipitation of Cu-enriched metallic compound under different aging temperatures were determined to be the predominant strengthening mechanisms controlling the variation trend of mechanical properties corresponding to different aging temperatures with respect to 15-5 PH stainless steel.

The research described here was aimed at illuminating the variation in the strengthening mechanism of Cr15Ni5 precipitation hardening stainless steel (15-5PH stainless steel) processed at aging temperatures ranging from 440–610 °C. The variation in the tensile property corresponding to different aging processes was measured, and the microstructure features were further characterized using a transmission electron microscope (TEM) and electron back-scatter diffraction (EBSD). Results indicated that the strength contribution induced by grain-refinement strengthening, precipitation strengthening and dislocation strengthening corresponding to different aging temperatures varying from 470–610 °C were determined to be distributed in strength ranges of 296–345 MPa, 0–469 MPa and 97–803 MPa, respectively. The strength increments caused by different combinations of precipitation strengthening and dislocation strengthening were crucial for determining the final mechanical properties of the studied 15-5PH stainless steel.

In order to illuminate the hindering effects induced by grain boundaries on the propagation behavior of crack with respect to 15‐5 PH stainless steel, interactions between propagated crack and typical grain boundaries, including the parent austenite grain boundary (PAGB), coincidence site lattice Σ3 grain boundary (CSL Σ3), packet grain boundary (PGB), and block grain boundary (BGB) are investigated at the atomic scale. Results indicate that the higher stress in the crack initiation (CI) stage and crack and grain boundary interaction (CGB) stage is required to drive the propagating crack in terms of the PAGB model compared to the other models, and the longest interaction time between propagated crack and established grain boundary is needed for the crack from the crack propagation (CP) stage to the CGB stage in the case of the PGB model. The PAGB and PGB are determined to be the most effective in hindering crack propagation in 15‐5 PH stainless steel.

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