The alumina-boron carbide composites were prepared by sintering and hot pressing. the mechanical properties of hot pressed alumina-boron carbide composites are better than the inherent alumina matrix. a maximum fracture toughness, KIC, of 7.26 MPa·m1/2 is achieved for alumina-boron carbide whisker composites as is a 47% increase in flexural strength. the fracture toughness is dependent on the volume fraction of boron carbide. the lower thermal expansion coefficient of the composites as a function of boron carbide whisker content is shown.