Microstructures and strengthening mechanisms in high-carbon titanium-microalloyed interstitial-free steels

We report the mechanical properties and microstructures of titanium-microalloyed interstitial-free (IF) steels with different carbon contents smelted and rolled in the laboratory. The results show an increase of yield strength and tensile strength with carbon content, which are enhanced with lower coiling temperature (CT). Microstructure analysis reveals that the ferrite grain size varies from 11 to 23 mu m, while the average size of TiC as the main second-phase particle ranges from 10 to 35 nm. The sample with 80 ppm carbon and 853 K CT reaches a mechanical strength close to that of high-strength IF steels. The increase of yield strength is mainly attributed to both grain-refining and precipitation strengthening.