Microstructure and thermomechanical properties of Al11Ce3

This study investigates the microstructure and thermomechanical properties of the intermetallic compound Al11Ce3, which strengthens Al-Ce based eutectic alloys. Arc-melted bulk Al11Ce3, consisting of coarse, elongated grains oriented along the solidifying direction with internal twins, is hard and brittle at ambient temperature, with a microhardness of 4.3 +/- 0.3 GPa and indentation fracture toughness of 0.70 +/- 0.09 MPa m(1/2). The thermal expansion coefficient varies from 14 x 10(-6) /K (at 100 degrees C) to 32 x 10(-6) /K (at 600 degrees C). Al11Ce3 oxidation kinetics follow a parabolic law, with rates at/below 500 degrees C slow enough to enable long-term testing in air. Plastic creep deformation is extensive at 500 degrees C under uniaxial compressive loads; the strain rates follow a power-law with respect to stress with a stress exponent of 5.6, indicative of dislocation-controlled creep deformation, and with an activation energy of 276 +/- 29 kJ/mol (measured between 450 and 600 degrees C). The creep resistance of Al11Ce3 at 500 degrees C is similar to that of L1(2)-Al3Sc.