Thermal expansion, strength and oxidation resistance of Mo/Mo5SiB2 in-situ composites at elevated temperatures

Four Mo/Mo5SiB2 in-situ composites with different volume fractions of Mo solid solution, V-f(Mo), were produced by ingot metallurgy and their microstructure, thermal expansion, compressive strength and oxidation behavior were investigated relating to V-f(Mo). Mo-8.5Si-13.2B annealed at 2073 K for 24 h has nearly eutectic microstructure consisting of Mo solid solution and Mo5SiB2. to For higher V-f(Mo), there are micro-cracks in Mo5SiB2, phase probably induced by thermal stress during the cooling process. Mo-8.5Si-13.2B shows the highest yield stress among the four Mo/Mo5SiB2 in-situ composites, and about 1 GPa even at 1773 K. For lower V-f(Mo) than that of Mo-8.5Si-13.2B, the steady state oxidation behavior is observed at temperatures between 1173 and 1473 K, indicating that the oxidation resistance is relatively good, whereas the oxidation resistance is catastrophic for higher V-f(Mo) than that of Mo-8.5Si-13.2B. (C) 2003 Elsevier Ltd. All rights reserved.