Influence of Martensite Mechanical Properties on Failure Mode and Ductility of Dual-Phase Steels

Abstract

The effects of the mechanical properties of the martensite phase on the failure mode and ductility of dual-phase (DP) steels are investigated using a micromechanics-based finite element method. Actual microstructures of DP steels obtained from scanning electron microscopy (SEM) are used as representative volume elements (RVEs) in the finite element calculations. Ductile failure of the RVE is predicted as plastic strain localization during the deformation process. Systematic computations are conducted on the RVE to quantitatively evaluate the influence of the martensite mechanical properties and volume fraction on the macroscopic mechanical properties of DP steels. These properties include the ultimate tensile strength (UTS), ultimate ductility, and failure modes. The computational results show that, as the strength and volume fraction of the martensite phase increase, the UTS of DP steels increases, but the UTS strain and failure strain decrease. In addition, shear-dominant failure modes usually develop for DP steels with lower martensite strengths, whereas split failure modes typically develop for DP steels with higher martensite strengths. The methodology and data presented in this article can be used to tailor DP steel design for its intended purposes and desired properties.

Predicting Fracture Toughness of TRIP 800 Using Phase Properties Characterized by In-Situ High-Energy X-Ray Diffraction

“…In the microstructure shown in Figure 3(a), the bright area represents the ferrite phase and the dark area represents the dispersion of the bainite and retained austenite. After numerical image processing of Figure 3(a), a plane stress finite element model was generated, as shown in Figure 3(b), [16,17] which is used as the RVE of the TRIP 800 sheet steel in this study. Note that crystallographic texture is not included in our current 2-D model.…”

Characterization and Modeling of Manganese Effect on Strength and Strain Hardening of Martensitic Carbon Steels

“…necking strain). Principally, the mechanical behavior of martensite is described either with phenomenological polynomial law 6) or it is reduced to an elastic or an elastic-perfectly plastic law. 7) However, recently a Continuum Composite Approach (CCA) was proposed to predict the complete tensile curves of as-quenched martensitic steels.…”

Characterization and Modeling of Failure Initiation in Bainite‐Aided DP Steel

“…Recently, failure modeling in DP steels is a subject of interest for several research groups [17][18][19][20][21][22][23][24][25] . They approach the topic through different scientific methods.…”

“…They approach the topic through different scientific methods. Sun et al [17] and Choi et al [18] studied the failure mode and ultimate ductility of DP steels using a microstructure-based model in different loading and boundary conditions. In their studies, ductile failure was predicted as the result of plastic instability in the form of strain localization triggered by the microstructurelevel inhomogeneity between the hard martensite and ferrite phases.…”