A New Electron Backscatter Diffraction-Based Method to Study the Role of Crystallographic Orientation in Ductile Damage Initiation

Abstract

The third generation of advanced high strength steels shows promising properties for automotive applications. The macroscopic mechanical response of this generation can be further improved by a better understanding of failure mechanisms on the microstructural level and micro-mechanical behavior under various loading conditions. In the current study, the microstructure of a multiphase low silicon bainitic steel is characterized with a scanning electron microscope (SEM) equipped with an electron backscatter diffraction detector. A uniaxial tensile test is carried out on the bainitic steel with martensite and carbides as second phase constituents. An extensive image processing on SEM micrographs is conducted in order to quantify the void evolution during plastic deformation. Later, a new post-mortem electron backscatter diffraction-based method is introduced to address the correlation between crystallographic orientation and damage initiation. In this multiphase steel, particular crystallographic orientation components were observed to be highly susceptible to micro-void formation. It is shown that stress concentration around voids is rather relaxed by void growth than local plasticity. Therefore, this post-mortem method can be used as a validation tool together with a crystal plasticity-based hardening model in order to predict the susceptible crystallographic orientations to damage nucleation.

High-Strength Low-Alloy Steels

“…The macroscopic mechanical response of this new generation can be further improved by a better understanding of the failure mechanisms on the microstructural level under different service conditions. Shakerifard et al [21] conducted a comprehensive microstructural characterization of a multiphase low-silicon bainitic steel using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction detector. Concerning metallic structures operating in soils and natural waters, corrosion under the effect of a stray current is among the most hazardous types of damage.…”

Advanced Crystal Plasticity Modeling of Multi-Phase Steels: Work-Hardening, Strain Rate Sensitivity and Formability

“…As an example of possible techniques that could be applied, it is studied how strain inhomogeneities between different grains might be used to investigate the formability of the material. In [74,75], the crystallographic texture around voids in damaged material was identified and clearly differentiated from the texture of grains far from these voids. In [43], a correlation was found between the orientations of grains surrounding the voids and the orientations of the pairs of grains for which a maximum difference was observed in the shear stress component on the plane perpendicular to the loading direction.…”