PSI - Issue 69

Haofei Zhu et al. / Procedia Structural Integrity 69 (2025) 113–120

116

Fig. 2. (a-d) The SEM images of the samples after solid-solution treatment and (e)the corresponding changes in PAGs at different temperatures: (a) 870 °C; (b) 900 °C; (c) 930 °C; (d) 960 °C.

Fig. 3 (a) The XRD patterns of the samples after solid-solution treatment and (b) the corresponding variation in retained austenite content at different temperatures.

Fig. 4 shows the SEM images of the aged samples after different solid-solution temperatures treatment. Due to tempering of the martensite, the PAG, composed of martensitic packets, blocks, and laths, are clearly observable after etching. Consistent with the trend of changes in PAG, and due to the inheritance of austenite grains, the size of martensitic blocks also increases with rising solid-solution temperature. Notably, after solid-solution treatment at 870 °C followed by aging, spherical particles (blue arrows) observed within the martensitic laths and at their interfaces, as shown in Fig. 4(a). As the solid-solution temperature increases, the size and number of these spherical particles decrease at 900 °C. Above 930 °C, these spherical particles essentially disappear.