Tellurium Doping in MnS Inclusions and Corresponding Modification Effect: Experimental and First-Principles Study

Te is sulfide inclusion morphology optimization element in steel, and Te doping in MnS inclusions is considered the main mechanism for modification, but the mechanism of Te doping behavior itself is not clear. Te-doped MnS inclusion behavior in steel was investigated using optical microscope, electron probe microanalysis, transmission electron microscopy, thermomechanical simulator, and first-principles calculations. After Te treatment, the amount of type II sulfides was decreased, the size of sulfides was increased, and the sulfides were strengthened. The aspect ratio of hot deformed sulfides was decreased significantly through Te doping. The atomic ratio of S to Te for MnS inclusions with MnTe adhesion was determined to be between 66 and 49 through the energy and wavelength spectra. The crystal structure of the Te-doped MnS inclusions retained the rock-salt structure, and no ordered structure was formed. The first-principles calculation results showed that the doping of Te led to the replacement of S atoms from MnS. Lattice distortion was observed after Te doping, and the lattice constant increased; Te doping mainly affected the position of the nearest Mn atoms, and the lattice distortion can affect about three layers of atoms along the < 100 > direction. Considering the cost-effectiveness of adding Te, the mass ratio of Te to S should be controlled at approximately 0.063 during actual production.