The Prediction of the Mechanical Properties for Dual-Phase High Strength Steel Grades Based on Microstructure Characteristics

Abstract

The decrease of emissions from vehicle operation is connected mainly to the reduction of the car's body weight. The high strength and good formability of the dual phase steel grades predetermine these to be used in the structural parts of the car's body safety zones. The plastic properties of dual phase steel grades are determined by the ferrite matrix while the strength properties are improved by the volume and distribution of martensite. The aim of this paper is to describe the relationship between the mechanical properties and the parameters of structure and substructure. The heat treatment of low carbon steel X60, low alloyed steel S460MC, and dual phase steel DP600 allowed for them to reach states with a wide range of volume fractions of secondary phases and grain size. The mechanical properties were identified by a tensile test, volume fraction of secondary phases, and grain size were measured by image analysis. It was found that by increasing the annealing temperature, the volume fraction of the secondary phase increased, and the ferrite grains were refined. Regression analysis was used to find out the equations for predicting mechanical properties based on the volume fraction of the secondary phase and grain size, following the annealing temperature. The hardening mechanism of the dual phase steel grades for the states they reached was described by the relationship between the strain-hardening exponent and the density of dislocations. This allows for the designing of dual phase steel grades that are "tailored" to the needs of the automotive industry customers.

Mechanical Behavior of High-Strength, Low-Alloy Steels

“…In this Special Issue, attention is paid to the relation of the final mechanical properties and the microstructural features. The paper by Branco et al [1] provides an insight into the role of the bainitic morphologies in fatigue cyclic plastic properties; the paper by Liang et al [2] studies the effect of phase fraction on deformation and fracture behavior in low-carbon ferrite-martensite steels; and the paper by Evin et al [3] addresses the microstructure characteristics of the mechanical properties of dual-phase, high-strength steels.…”

Identification of Chaboche–Lemaitre combined isotropic–kinematic hardening model parameters assisted by the fuzzy logic analysis

“…Most of elastoplastic materials exhibit cyclic hardening or softening under the proportional strain-controlled cyclic loading [11][12][13][14]. Hardening defined as the increase of the yield stress in the wake of the plastic deformation shows that the yield function depends on: applied stress, the loading history, temperature, strain rate, and others [14,15]. Cyclic hardening and softening in various elastoplastic materials under straincontrolled cyclic loading have been widely investigated over the last few decades.…”

Modeling the Mechanical Response of a Dual-Phase Steel Based on Individual-Phase Tensile Properties

“…A micromechanical model that explains the influence of martensite fraction on the 0.2% proof stress was developed by Liedl and collaborators, carrying out three-dimensional finite element simulations and showing that there exists a work-hardened ferrite zone that has influence in the initial flow behavior of the steel [26]. More recently, Evin et al [27] modeled the yield strength, the uniform deformation and the true stress of DP steels based on both the volume fraction of secondary phases and the grain size of the ferrite grain. Crystal plasticity modeling was applied by Xu et al [28] to describe the response of DP steels taken into account that the volume fractions of the constituent phases and the strain partitioning function could be obtained by tensile experiments.…”