Phase-field Simulation of Habit Plane Formation during Martensitic Transformation in Low-carbon Steels

Abstract

The origin of the habit plane of the martensite phase (α ′) in low-carbon steels is elucidated by threedimensional phase-field simulations. The cubic → tetragonal martensitic transformation and the evolution of dislocations with Burgers vector a α ′ /2〈111〉 α ′ in the evolving α ′ phase are modeled simultaneously. By assuming a static defect in the undercooled parent phase (γ ), we simulate the heterogeneous nucleation in the martensitic transformation. The transformation progresses with the formation of the stress-accommodating cluster composed of the three tetragonal domains of the α ′ phase. With the growth of the α ′ phase, the habit plane of the martensitic cluster emerges near the (111) γ plane, whereas it is not observed in the simulation in which the slip in the α ′ phase is not considered. We observed that the formation of the (111) γ habit plane, which is characteristic of the lath martensite that contains a high dislocation density, is attributable to the slip in the α ′ phase during the martensitic transformation.

Influence of Material Parameters on Martensitic Transformation and Its Sensitivity Analysis

“…Anisotropy, the habit is a constant plane, which is consistent with the classic WLR and BM theory . In the last few decades, the phase field method has shown tremendous capabilities of predicting Martensitic phase transformation . When the martensite transformation model is solved based on the phase field method, the values of various parameters will directly affect the final calculation results.…”

Phase-field Modeling and Simulation of Solid-state Phase Transformations in Steels

“…Later, the phase-field modeling of lath martensite formation in low-carbon steels, which is different from the above-mentioned models, 80,82) was developed by Murata and co-workers. [83][84][85][86][87] They proposed a new theory of plastic accommodation in the martensitic transformation by considering the slip deformation in the martensite phase, which was named the "two types of slip deformation" (TTSD) model. Using the TTSD model, it was shown theoretically for the first time that the hierarchical structures of lath martensite and the KS variants are formed as a result of slip deformation in the martensite phase.…”

“…5, Tsukada et al demonstrated that the elastoplastic phase-field model based on the TTSD model reproduces the formation of a (111) habit plane during lath martensite formation. 85) Subsequently, the phase-field model was also applied to the modeling of lath martensite recovery. 87) In the future, further development of the phase-field model is expected for the quantitative prediction of not only lath martensite formation, but also other martensite morphologies in polycrystalline austenite.…”

Formation Mechanism of Lath Martensite in Steels

“…As mentioned above, the morphology of the lath martensite can be characterized by the plastic deformation accompanying dislocation slips, indicating that the maximum dislocation density is evaluated from the plastic strain caused by martensitic transformation. During the transformation, the dislocation density is considered to involve dislocations existing in the austenite phase around the martensite phase because if plastic strain arises in the austenite phase around the transformed martensite phase, the constraint force from the surrounding austenite phase to the newly formed martensite phase decreases, thereby decreasing the plastic strain in the newly formed martensite phase 56) . In other words, the total strain caused by martensitic transformation corresponds to the value in Fig.…”