Effects of Microstructural Morphology on Formability, Strain Localization, and Damage of Ferrite-Pearlite Steels: Experimental and Micromechanical Approaches

Abstract

This paper attempts to predict how the microstructural features and mechanical properties of the individual constituents affect the deformation behavior and formability of ferrite-pearlite steels under quasi-static loading at room temperature. For this purpose, finite element simulations using representative volume elements (RVEs) based on the real microstructures were implemented to model the flow behavior of the ferrite-pearlite steels with various microstructural morphologies (non-banded and banded). The homogenized flow curves obtained from the RVEs subjected to periodic boundary conditions together with displacement boundary conditions were validated with the experimental results of the uniaxial tensile tests. Then, the initial microstructural inhomogeneity and Johnson-Cook damage criteria were employed for both non-banded and banded RVEs to estimate the onset of plastic instability under different loading paths ranging from uniaxial tension to equi-biaxial tension. Finally, the forming limit diagrams of both ferritic-pearlitic microstructures were predicted, which show a good agreement with the experimental results of the Nakazima stretch-forming tests (less than 13 pct error). It implies that the initial microstructural inhomogeneity criterion adequately enables to predict the plastic instability in the ferritic-pearlitic steel sheets without using any damage or failure criterion. The most commonly observed damage mechanism is the severe plastic deformation of the ferrite grains near the pearlite colonies due to the strength contrast between ferrite and pearlite. Another significant finding is that the microstructural morphology has a crucial influence on the strain partitioning, strain localization, and formability of the ferritic-pearlitic steels.

Thermomechanical Analysis of Ceramic Composites Using Object Oriented Finite Element Analysis

“…More recently, a study was performed on ferritic-pearlitic based steel and found that the predicted results was in good agreement with the experimental results [31]. They found that the microstructural morphology plays a vital role in strain partitioning, strain localization and formability of the ferritic-pearlitic steels [31].…”

“…It can be said that the OOF2 provides a better transition between the mechanical/thermal behavior of a heterogeneous material at the macro-scale and the mechanical/thermal response of its constituent phases. It provides adequate information about microstructures/ phases (volume fraction, distribution, orientation) to ensure a realistic assessment of thermo-mechanical properties [30][31][32]. More recently, a study was performed on ferritic-pearlitic based steel and found that the predicted results was in good agreement with the experimental results [31].…”

“…It provides adequate information about microstructures/ phases (volume fraction, distribution, orientation) to ensure a realistic assessment of thermo-mechanical properties [30][31][32]. More recently, a study was performed on ferritic-pearlitic based steel and found that the predicted results was in good agreement with the experimental results [31]. They found that the microstructural morphology plays a vital role in strain partitioning, strain localization and formability of the ferritic-pearlitic steels [31].…”

Characterization of Microstructural Damage and Failure Mechanisms in C45E Structural Steel under Compressive Load

“…The results presented in the study by Brandaleze [26] show that an increased proportion of ferrite in the microstructure (or a decrease in the carbon content of steel) prevents a decrease in the distance between the cementite lamellae in pearlite, which has a negative effect on the ductility. In addition, the crystal grain size [27], microstructural morphology [28], micro alloying [29] and distance between cementite lamellae [30,31] have a strong influence on the mechanical properties and formability/workability of ferritic-pearlitic steels. In general, it can be said that a microstructure that increases material strength tends to reduce ductility, and vice versa.…”

“…However, in their case, the dominant nucleation mechanism took place in the soft ferritic base. Based on tests performed under different tensile stress conditions (from uniaxial to biaxial plane tension), Isavand and Assempour [28] found that microstructural damage is mostly caused by considerable plastic deformation of ferrite grains located near pearlite colonies. Intense plastic deformation of ferrite grains is a consequence of a severe deformation incompatibility between the soft and hard phases (ferrite and pearlite).…”