Yield strength enhancement of martensitic steel through titanium addition

Yield strength enhancement for martensitic steel fabricated by vacuum induction melting is investigated. It is found that the addition of Ti can improve the yield strength property of the martensitic steel, which can be attributed to increase in precipitation hardening from formation of TiC precipitates in the martensitic matrix. Moreover, the yield strength can be further enhanced by tempering and reheat quenching process, which can be ascribed to the formation of a superfine sized (~8 μm) grains and large amount of freshly nano-sized (1–10 nm) precipitates in the final martensitic structure for martensitic steel containing Ti. The experimental and theoretical results on the contribution of TiC precipitates to hardening of the martensitic steel are in excellent agreement, showing that the precipitation hardening of 188 MPa caused by TiC precipitates is the main reason why the yield strength for martensitic steel is enhanced via titanium addition.