Effect of strain-induced precipitation on microstructure and properties of titanium micro-alloyed steels

The strain-induced precipitation behavior of titanium micro-alloyed steel was examined through the stress relaxation method. In addition, the relationship between strain-induced precipitation and isothermal precipitation was explored. The findings revealed that the strain-induced precipitation and recrystallization processes of titanium micro-alloyed steel coexist and compete at the same time. The results also showed that the recrystallization process was inhibited with strain-induced precipitation. Moreover, a large amount of nano-sized TiC particles precipitated in Ti micro-alloyed steel. Notably, the strain-induced precipitated TiC had a size of 10 nm and isothermally precipitated TiC had a size of 3–6 nm. Additionally, there was a clear competitive relationship between strain-induced precipitation and isothermal precipitation. The findings also showed that strain-induced precipitation had an obvious effect on the refinement of austenite although the effect was not obvious on the increase in the yield strength. Furthermore, isothermal treatment was shown to be more advantageous than strain-induced precipitation. Finally, the major increase in the yield strength was mainly attributed to the precipitation strengthening of nano-sized TiC during isothermal precipitation.