STUDY ON THE PREPARATION PROCESS OF T2 ALLOY IN THE Mo-Si-B SYSTEM

Mo5SiB2 (T2) can be used as a promising elevated-temperature structural material because of its high melting temperature (about 2200 degrees C), and excellent resistance to oxidation and creep. The Mo5SiB2 (T2) alloy was prepared by both spark plasma sintering (SPS) and tube furnace sintering (TFS), and then the microstructures were characterized by XRD, SEM-EDS and TEM. The results show that the rapid heating rate is one of important dynamic conditions responsible for the synthesis of T2. Compared with traditional methods, SPS can provide the fast synthesis in a particular way of labilized plasma sintering so that the sample can be heated to the expected temperature of 1500 degrees C with a short period. The melted Si can rapidly react with Mo and B to synthesize T2 in the solid-liquid state prior to the formation of binary phases (Mo3Si, Mo5Si3, MoB, etc.) in the solid state in the range of 600 similar to 1200 degrees C. The average size of grains is equal to 1.44 mu m. The boundaries are clear and have the shape of a straight line without transition zones. Moreover, no defects such as dislocations were found in the T2 alloys prepared by SPS.