Ti‐Nb Synergistic Precipitation: Enhancing Grain Refinement and Dislocation Strengthening in Advanced Ultralow‐Carbon Automotive Microalloyed Steels

To provide a reference for the chemical composition design of combined Ti‐Nb microalloyed steels, four ultralow‐carbon microalloyed steels with different Ti contents were prepared to study the microstructural characteristics and mechanical property by using transmission electron microscope (TEM), X‐ray diffraction (XRD), and tensile equipment. The results show that an increase in Ti content enhances the material strength but reduces the total elongation after fracture. All steels contain {110}<110>, {110}<001>, and {112} textures, and with the increase in Ti content, the {100}<001> texture is gradually formed. The microstructure characterization discloses that the grain size decreases with the increase in Ti content, and the underdeveloped pearlite characterized by precipitation of Fe 3 C, Fe 2 C, and FeC are found in samples both with low and high Ti contents. It is revealed that the combined addition of Nb and Ti can significantly enhance the precipitation strengthening and dislocation strengthening effects, but it does not change the main mechanisms of precipitation‐driven fine‐grain and dislocation strengthening. It is estimated that the average yield strength shows a total 40.9% rise from alloying 0.03 wt% Ti to 0.113 wt% Ti in the steels, and the combined addition of 0.01 wt% Nb can increase the yield strength by approximately 60–70 MPa.