Effect of Ti Content on Microstructure Evolution and Mechanical Properties of High-Strength Anti-seismic Rebar

The microstructure, precipitates, fracture morphology, and mechanical properties of both the Ti microalloyed rebars during the rolling process and the final product were characterized using optical microscopy, scanning electron microscopy, transmission electron microscopy, and a universal tensile testing machine. The results indicated that the precipitation of Ti in deformed austenite can inhibit the recrystallization of austenite and refine its grains. The stability of undercooled austenite improves with an increase in Ti content, leading to a reduction in the transformation temperature of ferrite (F) and pearlite (P), refinement of the microstructure, and promotion of bainite (B) transformation. The reduction in F grain size and increase in B are advantageous for improving the strength and tensile/yield of rebars. However, the elongation at maximum force and elongation after fracture decrease. When the Ti content exceeds 0.06%, the strength change of the rebar is primarily governed by the B. A continuous increase in stress during the tensile process, the disappearance of the yield plateau, and a decrease in ductility are caused by the increase in dislocation density and precipitates in the rebar. Better mechanical properties are exhibited by the rebar when the Ti content is 0.028%.