Effect of nano-sized TiC particle addition on microstructure and mechanical properties of SA-106B carbon steel

The dispersion behavior of nano-sized TiC particles treated by different processes and its influence on microstructural and mechanical modification has been investigated in SA-106B carbon steel with different TiC contents. It was found that mechanically-activated TiC nanoparticles introduced into a carbon steel matrix were dissolved during hot rolling and re-precipitated vigorously during subsequent normalizing treatment at 920 °C. The dispersed TiC particles were very fine (<20 nm), giving a suppressing effect on the growth of recrystallized austenite to promote considerable grain refinement of final ferrite-pearlite structure. This fine microstructure (grain size: ~10 μm) with a homogeneous distribution of TiC particles offers a higher strength level (yield strength: 372 MPa, tensile strength: 544 MPa) without sacrificing ductility (>30%) and impact energy (>250 J) at the TiC content of 0.1 wt%. Theoretical calculations showed that grain refinement plays a dominant role in enhancing the yield strength of TiC-bearing carbon steel, together with nanoparticle strengthening interacting on the solid solution strengthening and dislocation strengthening.