Effect of Vanadium Microalloying on the Mechanical and Microstructural Behavior of Moroccan Reinforcing Steels for Seismic Applications

Seismic-resistant reinforcing steels play a key role in structures subjected to earthquake loading, requiring an optimal balance between strength, ductility, and weldability. Microalloying with vanadium (V), niobium (Nb), and titanium (Ti) is widely used to improve these properties through precipitation strengthening and grain refinement. This work aims to contribute to the development of seismic-resistant reinforcing steels for the Moroccan construction sector. A literature review identified key international requirements, including a tensile-to-yield strength ratio (Rm/Re) of 1.15–1.35 and a total elongation at maximum force (Agt ≥ 7%). In parallel, Moroccan reinforcing bars were mechanically and microstructurally characterized. A conventional steel containing 0.65 wt.% Mn and no vanadium was used as a reference. This steel exhibited limited strain-hardening capacity, with Rm/Re ratios between 1.12 and 1.15. To improve this behavior, steels containing 1.1 wt.% Mn with different vanadium additions were investigated. Preliminary results indicate that vanadium microalloying improves mechanical performance through combined precipitation strengthening and ferrite grain refinement. The increase in strength is likely associated with fine V(C,N) precipitates formed during cooling, while ferrite grain refinement appears to contribute to maintaining ductility. This synergistic effect results in a more favorable strength–ductility balance, supporting the development of seismic-resistant reinforcing steels for structural applications.