Regular Article

Stretching the mechanical properties in a 590 MPa ferrite-martensite dual-phase steel through rapid heating

¹ State Key Laboratory of Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819, PR China
² Department of Metallurgical, Materials and Biomedical Engineering and Center for Structural and Functional Materials Research and Innovation, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968, USA

^* Email: dhshuang@mail.neu.edu.cn

Received: 14 October 2016
Received in final form: 16 February 2017
Accepted: 17 May 2017

Abstract

In the study described here, rapid heating was adopted to obtain ferrite/martensite dual-phase (DP) steels. An understanding of structure-property relationship was obtained through electron microscopy. The average ferrite grain size of steel with heating rate of 300 °C/s (HRA) was refined from 10.2 µm to 4.3 µm as compared to the conventional heating rate of 5 °C/s (CA) during continuous annealing. The morphology of martensite was changed from network-type along the ferrite grain boundaries to uniform distribution in the final DP microstructure. The HRA steel exhibited excellent mechanical properties, R_m = 712 MPa, R_p0.2 = 438 MPa, UEL = 15.7% and TEL = 23.3% and the product of strength and ductility (R_m × TEL) is 17,650 MPa %. In comparison to the conventional continuous annealed steel (CA), there was 8.4% increase in ultimate tensile strength and 10.4% increase in total elongation. The variations of strength, elongation, strain hardening behavior and fracture mechanism for steel subject to different heating route are discussed in relation to the microstructure.