Effect of Ti content on preparation and properties of TiB₂-SiC-Ti materials

Abstract

Since the 21st century, low atomic number material coating has been considered as one of methods for treating the first wall of controllable thermonuclear fusion device . The TiB₂ material with high melting point, high hardness, low coefficient of thermal expansion, excellent wear resistance and low atomic number has entered into people’s field of vision. Single TiB₂ is difficult to sinter and process into other products. Therefore, adding ceramic and metal additives to TiB₂ matrix material to effectively improve the mechanical properties and processability of the material has become a research hotspot. On the basis of the existing researches of TiB₂-SiC, in the present work the metal Ti powder is added as the second additive to improve the properties of TiB₂ composite. The TiB₂ and SiC are mixed at a mass ratio of 2 to 3, then two kinds of TiB₂-SiC-Ti materials with different amounts of Ti content are prepared by spark plasma sintering (SPS) technology. The materials are irradiated by a He⁺ beam with energy of 60 keV and ion fluence of 2 × 10¹⁷ ions/cm² at room temperature. The material is heat-treated at 1500 ℃ before and also after irradiation. The performances of prepared samples, the effect of irradiation on materials and the results of high temperature heat treatment are characterized by energy dispersive spectroscopy, Raman spectrum, grazing angle x-ray diffraction spectrum, Vickers hardness, wear resistance test, and scanning electron microscope. The results show that the surface morphology and toughness of TiB₂-SiC-Ti material with 3% Ti mass fraction are poor as shown in SEM images. The wear resistance test indicates that the material surface is seriously worn and the wear resistance is poor. The X-ray diffraction spectrum and Raman spectra show that the material is oxidized seriously at 1500 ℃, which is likely to be the cause of the poor compactness of materials. Raman spectra, Grazing angle X-ray diffraction spectrum and some Vickers hardness data before and after irradiation indicate that the material with low Ti content possess better crystal structure and weaker irradiation hardening. In conclusion, the TiB₂-SiC-Ti material with 3% Ti mass fraction exhibits lower density, poorer wear resistance and lower hardness, while the material with lower Ti mass fraction is more resistant to irradiation than the material with 6% Ti mass fraction at room temperature.