Flow Behavior and Microstructure of a Mo–V–Ti Micro-Alloyed High-Strength Steel

Flow behavior and microstructure characteristics of a Mo–V–Ti micro-alloyed high-strength steel were investigated through hot compression tests with two procedures. In group 1, the specimens were quenched after deformation at temperature range of 800–1100 °C, with strain rate of 10/s. Initiation of dynamic transformation (DT) and dynamic recrystallization (DRX) were confirmed by the evolution characteristics of work hardening rate (θ) during deformation. Critical stresses of both DT and DRX decreased with the increase in deformation temperature. The critical strain for DRX also decreased with the increase in temperature, while the critical strain of DT was less temperature dependent. In group 2, with different holding times at 630 °C after 3-pass deformation, complex precipitates were acquired from all the specimens. For the specimen that was water quenched after deformation, the particles were as fine as 20 nm. For the specimens that were held at 630 °C for 30–120 min, the particles were around 100–200 nm. Mo content in the precipitates decreased with holding time at 630 °C. V content in the particles is much less than Ti content because the Gibbs free energy of TiC is less than that of VC at the same temperature.