Strain Hardening Behavior of Dual-Phase Steels

Abstract

A detailed qualitative and quantitative examination of the microstructure and mechanical properties of three different classes of DP600 and DP450 dual-phase (DP) steels was carried out. The tested DP steels are characterized by different alloying elements: aluminum, boron, and phosphorus. Among them, aluminum DP steels showed the lowest percentages of hard phases, while phosphorus DP steels exhibited the highest resistance values. The Hollomon, Pickering, Crussard-Jaoul (CJ), and Bergstrom models were used to reproduce the strain hardening behavior of DP steels. Relationships that correlate the fitting parameters with the chemical composition and the thermal cycle parameters were found, and the predictive abilities of different models were evaluated. The Pickering equation, among the tested models, is the best one in the reproduction of the experimental stress-strain data.

Use of the Aging Effect to Change the Local Properties of Structure Components

“…Multiphase steels have proved a good compromise between strength and ductility [7][8]. The multiphase steels exhibit a continuous yielding behavior, low yield point, and a high strain-hardening coefficient [9][10]. This has been attributed to an increase in the work hardening limits through forming mobile dislocations due to the martensite transformation during heat treatment and martensite twinning during forming [11][12].…”

Prediction of Continuous Cooling Transformation Diagrams for Dual-Phase Steels from the Intercritical Region

“…Figure 13 compares the tensile and yield strengths predicted by Eqs. [17] and [18] with the experimental ones. The relative error and the average error percentages for the used dataset are also reported.…”

“…In the same work, a model based on Avrami's equation and Scheil's additivity principle for predicting only the kinetics of austenite to ferrite transformations in multiphase steels from intercritical temperature was developed by Murugaiyan et al [5] Moreover, for dual-phase steels that are often used in the stamping process, mathematical models were developed for predicting their strain-hardening from chemical composition and process parameters. [17] In addition to the present literature for these kinds of steels, the model developed in this work is able to reproduce well all the microstructural transformations occurring during cooling in order to better predict their final microstructure and mechanical properties and provide a useful tool for the steel industry.…”

Untitled

“…Continuous yielding was observed for all the samples given this particular treatment, which is a common characteristic of regular dual phase steels. Austenite to martensite transformation involves volume expansion which introduces .doi.org/10.22161/ijaers.4.8.1 ISSN: 2349-6495(P) | 2456-1908(O) www.ijaers.com Page | 7 residual stress on the surrounding ferrite as a result of the strain produced during the transformation [25,26,27]. Davis (1979) [28] and Rigsbeeet al (1979) [29] Fig.6 shows that tempering the as-quenched intermediately quenched sample at 320 O C for 1hr decreases hardness (IQT series).…”