Thermodynamic Analysis on Precipitation Behavior of Titanium-containing Precipitated Phases of Titanium-alloyed High Boron Steel

The precipitation behavior of the titanium-containing precipitated phases of titanium-alloyed high boron steel in liquid phase and during solidification has been studied by thermodynamic calculation and experiments.Solidification microstructures of the high boron steel were researched by means of optical microscope(OM),scanning electron microscope(SEM),X-ray diffractometer(XRD).The results show that the solidification microstructures of cast alloy without alloying with Ti consist of boride,ferrite, and pearlite,and boride successively distributes along grain boundary in reticular form,while the microstructures of titanium-alloyed cast alloy consist of second-phase TiC,boride and matrix.Thermodynamic calculation results show that the titanium-containing precipitated phases cannot precipitate in the liquid phase; TiC can precipitate at 1691K when the solidification volume fraction reaches 29% during its solidification,and the precipitation sequence of the precipitated phases is TiC > TiB₂> TiB.