Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching-Partitioning-Tempering Steels

The orientation relationships (ORs) between the martensite and the retained austenite in low- and medium-carbon steels after quenching-partitioning-tempering process were studied in this work. The ORs in the studied steels are identified by selected-area electron diffraction (SAED) as either K-S or N-W ORs. Meanwhile, the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto. The simulated K-S and N-W ORs in the low-index directions generally do not well coincide with the experimental pole figure, which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions. However, the simulated results coincide well with experimental pole figures in the high-index directions {123}(bcc). A modified method with simplicity based on Miyamoto's work was proposed. The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto' method, that is, the OR is near K-S OR for the low-carbon Q-P-T steel, and with the increase of carbon content, the OR is closer to N-W OR in medium-carbon Q-P-T steel.