Microstructure-Based Modeling of the Effect of Inclusion on the Bendability of Advanced High Strength Dual-Phase Steels

Abstract

Advanced high strength dual-phase steels are one of the most widely sought-after structural materials for automotive applications. These high strength steels, however, are prone to fracture under bending-dominated manufacturing processes. Experimental observations suggest that the bendability of these steels is sensitive to the presence of subsurface non-metallic inclusions and the inclusions exhibit a rather discrete size effect on the bendability of these steels. Following this, we have carried out a series of microstructure-based finite element calculations of ductile fracture in an advanced high strength dual-phase steel under bending. In the calculations, both the dual-phase microstructure and inclusion are discretely modeled. To gain additional insight, we have also analyzed the effect of an inclusion on the bendability of a single-phase material. In line with the experimental observations, strong inclusion size effect on the bendability of the dual-phase steel naturally emerge in the calculations. Furthermore, supervised machine learning is used to quantify the effects of the multivariable input space associated with the dual-phase microstructure and inclusion on the bendability of the steel. The results of the supervised machine learning are then used to identify the contributions of individual features and isolate critical features that control the bendability of dual-phase steels.

Correlating Prior Austenite Grain Microstructure, Microscale Deformation and Fracture of Ultra-High Strength Martensitic Steels

“…In summary, we have shown that even though the uniaxial stress-strain response of the low-carbon martensitic steel is not very sensitive to the variations in the heat-treatment parameters, their fracture response differs significantly. This is similar to dual-phase steels, for which it has been shown that the interaction of the heterogeneous deformation fields induced by the geometry of deformation, i.e., the presence of a notch in the single-edge notch specimens or three-point bending, and the material microstructure, i.e., distribution of a hard (martensite) and soft (ferrite) phases leads to an increase in the propensity of deformation localization, which significantly affects the fracture response of these materials [39][40][41]. The complex interactions of heterogeneous material microstructures and imposed loading conditions, and their effects on the observed mechanical response of materials, have also been observed under a host of other circumstances [42][43][44].…”