Effects of Re- and Al-alloying on mechanical properties and high-temperature oxidation of MoSi2

Alloying with Re and Al improves high-temperature strength and low-temperature ductility of MoSi2, respectively. The effects of Re + Al on strength and ductility of MoSi2 is the combination of their individual effects, resulting in an alloy whose BDTT is lowered to room temperature and whose strength at 1600 °C is enhanced by better than one order of magnitude. However, the effects of these alloying elements on oxidation resistance of MoSi2 were not as promising as the effects on mechanical properties. Alloying with 2 at% Al resulted in acceleration of the oxidation rate of MoSi2 by about one order of magnitude, whereas alloying with 1 at% Re had little or no effect on oxidation rate at 1400–1700 °C. Moreover, alloying MoSi2 with 1 at% Re + 2 at% Al resulted in deterioration of the high-temperature oxidation resistance of MoSi2 beyond the effects of Al alone.

► Alloying MoSi2 with 2.5 at% Re improves its high-temperature strength significantly. ► Alloying MoSi2 with 2 at% Al improves its low-temperature ductility significantly. ► Alloying MoSi2 with 1 at% Re + 2 at% Al improves its low-temperature ductility and high-temperature strength concurrently. ► Alloying MoSi2 with 2 at% Al results in degradation of its oxidation resistance. ► Although 1 at% Re does not affect the oxidation resistance of MoSi2 significantly, when added to 2 at% Al-containing MoSi, it results in accelerated oxidation.