Effect of Cr and Al additions on the development of interphase-precipitated carbides strengthened dual-phase Ti-bearing steels

The development of Ti-Cr-bearing hot-rolled dual-phase steel with an excellent combination of mechanical properties (yield strength of 655 MPa, ultimate tensile strength of 911 MPa, and elongation of 30%) has been achieved. Due to the significant strengthening obtained from interphase-precipitated nanometer-sized carbides in ferrite, this dual-phase steel has yield ratio of about 0.72, which is much higher than that of conventional dual-phase steels. Isothermal transformations on a dilatometer have been performed to investigate the effect of Cr and Al additions on austenite-to-ferrite transformation in Ti-based steels. It was found that an addition of 0.6 wt.% Cr obviously retards the transformation rate of ferrite, as compared with an addition of 0.1 wt.% Al. The results from dilatometry and transmission electron microscopy revealed that due to the lower transformation rate in Ti-Crbearing steel, a much higher density of nanometer-sized interphase-precipitated carbides in ferrite occurred during the isothermal holding at 650 C, leading to a significant increase in the strength of ferrite. (C) 2017 Elsevier Ltd. All rights reserved.