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

• Published in: Materials & design Vol. 119; pp. 319 - 325
• Main Authors: Tsai, Shao-Pu, Su, Te-Cheng, Yang, Jer-Ren, Chen, Chih-Yuan, Wang, Yuan-Tsung, Huang, Ching-Yuan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05-04-2017
• Subjects: Dilatometry; Dual-phase steel; Interphase-precipitated nanometer-sized carbide; Isothermal transformations; Transmission electron microscopy; Yield ratio; Dual-phase steel; Isothermal transformations; Interphase-precipitated nanometer-sized carbide; Dilatometry; Transmission electron microscopy; Yield ratio
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2017.01.071

The development of Ti-Cr-bearing hot-rolled dual-phase steel with an excellent combination of mechanical properties (yield strength of 655MPa, ultimate tensile strength of 911MPa, 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 0.6wt.% Cr obviously retards the transformation rate of ferrite, as compared with an addition of 0.1wt.% Al. The results from dilatometry and transmission electron microscopy revealed that due to the lower transformation rate in Ti-Cr-bearing 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.
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•A hot-rolled Ti-Cr-bearing interphase precipitation strengthened dual-phase steel has been developed.•Significant strengthening of interphase precipitation in ferrite leads to high yield ratio of about 0.72.•Isothermal heat treatments with transmission electron microscopy analyses have been conducted to examine Cr or Al effects.•Control of the intercarbide spacing is vital for the development of interphase precipitation strengthened dual-phase steels.