V 미세 첨가 TWIP강의 미세 조직과 기계적 물성에 관한 연구

Abstract

High tensile strength TWIP steel is an attractive automotive material as its use could result in improved fuel efficiency and passenger safety. Despite its high tensile strength, TWIP steel has a relatively low yield strength and this has been recognized as an important issue for passenger safety. To solve this problem, micro-alloying has been adopted to prevent grain growth, suppress the recrystallization of austenite and enhance the yield strength by carbide precipitation. In this study, microstructural analysis and mechanical testing were carried out on hot rolled high-Mn TWIP steels to which 0-0.31wt% vanadium was added. The vanadium additions contributed to a reduction of the grain size and yielded vanadium precipitates with varying distributions and compositions. The mechanical properties of the steel were evaluated by tensile tests and a yield strength increase of 413MPa / wt% added V was measured. The strengthening mechanisms in the vanadium micro-alloyed TWIP steel were analysed in detail taking into account the various microstructural contributions of the vanadium addition. Constitutive equations for the yield strength and strain hardening were derived to estimate the effect of vanadium addition in terms of the various strengthening mechanisms.