Improving mechanical and thermal expansion properties of aluminum matrix composites reinforced by silicon carbide fiber

Combining the colloidal dispersion method with the squeeze melt infiltration technique, aluminum matrix composites with different volume fractions of silicon carbide fiber were fabricated at 680 degrees C under vacuum. Microstructure analysis found that composite presented a dense structure and fibers were homogeneously distributed in matrix. The hardness, yield strength and elastic modulus of the composite monotonically increased with increasing the volume fraction of fiber. The highest flexural strength for composite with 10 vol% SiC fiber was achieved. The improved mechanical properties could be attributed to the dispersion strengthening and enhanced load transferring ability by fibers as well as the dislocation strengthening. On the other hand, the coefficient of thermal expansion of composites was measured at temperature up to 400 degrees C. It was found that the uniform introduction of silicon carbide fiber could significantly low the CTE of aluminum matrix composite, which could be attributed to the low CTE of SiC fiber and good fiber-matrix interface bonding.