Oxidation behavior of AlMgB14-TiB2 composite at elevated temperature

The isothermal oxidation behavior of AlMgB14-TiB2 composite was investigated at the temperature range from 600 °C to 1000 °C in air for 10 h. The results showed that the oxidation kinetics of this composite obeyed the parabolic law with an activation energy of 176 ± 20 kJ mol−1 from 700 °C to 1000 °C, the corresponding parabolic rate constant increased from 0.0069 × 10−8 kg2 m−4 s−1 to 138.75 × 10−8 kg2 m−4 s−1. The SEM micrograph of the oxidized surface at 700 °C for 10 h indicated that only the TiB2 phase was changed. The AlMgB14 phase changed at 800 °C in air, and the oxide scale consisting of TiO2 and borate glass dissolved with MgO and Al2O3. Meanwhile, a number of pores also existed in the oxide scales. The oxide scales at 1000 °C were divided into three layers: an outer glassy B2O3 layer, a middle oxide layer with small size pores, and a reaction layer with large size pores formed as the oxidation of the AlMgB14 phase. The formation mechanism of the oxidized layers was analyzed.