Paper number 568

MECHANICAL PROPERTIES OF MOSI2-AL2O3 COMPOSITES PROCESSED BY SHS

A.L. Dumont, J.P. Bonnet, and C. Gault

Groupe d'Etudes des Matériaux Hétérogènes, ENSCI
47 Avenue Albert Thomas, 87065 Limoges, France

Summary

MoSi2-Al2O3 composites have been processed using a SHS technique assisted by the application of a low uniaxial pressure to achieve densification. MoSi2 - rich composites (21 vol.% Al2O3), intermediate composition (56.1 vol.% Al2O3) and Al2O3 - rich composites (68.1 vol.% Al2O3) have been fabricated. In this paper, their mechanical properties (elastic moduli and creep behaviour) are investigated and discussed considering microstructure. Young's and shear moduli have been measured using an ultrasonic pulse-echo method. Their zero porosity values, extrapolated from experimental results are found to be inferior to the theoretical values predicted by a two-phase model. This is attributed to the influence of intergranular phases and/or microcracks. Compressive creep measurements have been performed in air in the 50-200 MPa and 1150-1400°C ranges. Pseudo-stationary stages are observed with two different regimes characterised by different stress exponent values depending on the stress level.

Keywords

elasticity, ultrasonics, creep, molybdenum disilicide, alumina, self heating synthesis.