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The aim of this study was to investigate the effect on high temperature of mechanical properties of adding Al 2 O 3 particles to polycrystalline Mo(Si,Al) 2. Mo(Si,Al) 2 -Al 2 O 3 composites, containing 0–25 wt% Al 2 O 3 particles have been compression tested at 1300 °C, and the microstructure after deformation was studied using electron backscatter diffraction. It was shown that even small amounts (5 wt%) of Al 2 O 3 particles resulted in a grain-refined material through inhibition of grain growth during sintering, which lead to lower flow stresses compared to the coarse-grained Al 2 O 3 -free material. The inverse grain size effect and post-test microstructure investigations suggest that creep-like deformation mechanisms dominate in fine grained Mo(Si,Al) 2 -Al 2 O 3 composites at 1300 °C. In the materials containing 5–15 wt% Al 2 O 3 , the maximum stress decreased with increasing Al 2 O 3 content. In materials with higher Al 2 O 3 additions, the maximum stress increased with the Al 2 O 3 addition, but did not reach the strength levels in the Al 2 O 3 -free reference material. It is suggested that the deformation behaviour is affected by electroplasticity effects as resistive heating was used. Electroplasticity contributes to the decrease in maximum stress observed in the lower Al 2 O 3 containing materials, while this is outweighed by particle strengthening at higher Al 2 O 3 contents. • Hot compression testing of Mo(Si,Al)-Al 2 O 3 composites with varying Al 2 O 3 content. • Al 2 O 3 particles decrease the grain size and reduce the strength. • Minimum strength was observed for intermediate Al 2 O 3 content. • Competing effects of particle strengthening and electroplasticity is suggested. [ABSTRACT FROM AUTHOR]

Polycrystalline Mo(Si,Al) 2 with C40 crystal structure was deformed in compression with a strain rate of 10−4 s−1 at 1300 °C. The specimens were deformed to a strain of 10%–15% and showed maximum stresses around 150 MPa prior to pronounced softening. No crack formation or significant increase in porosity could be observed. Post-test microstructure analysis revealed that the material was inhomogeneously deformed on both inter- and intragranular levels. Dynamic recrystallization occurred alongside low angle grain boundary formation in highly deformed grains. Furthermore, complex intragranular deformation fields suggest that slip systems other than 2 1 ̄ 1 ̄ 0 [0001] may be active during deformation. • Polycrystalline Mo(Si,Al) 2 was compressed to plastic strains above 10% at 1300 °C without crack formation. • The plastic strain is inhomogeneous on both inter and intragranular levels. • Low angle grain boundaries were formed in highly deformed grains. • Dynamic recrystallization occurs during deformation. [ABSTRACT FROM AUTHOR]