Mechanical properties of cBN-Al composite materials

The relationship between microstructure and mechanical properties for a wide range of composite materials based on polycrystalline cubic boron nitride and aluminium as a binder phase (PcBN-Al) has been examined. The PcBN-Al composites were made using high-pressure, high-temperature (HPHT) sintering methods, yielding materials with grain sizes of cBN between 2 and 20 m and an initial amount of Al binder between 15 and 25 vol.%. Hardness ranged between 15 and 40 GPa, while fracture toughness and strength were between 6.4-8.0 MPa m1/2 and 355-454 MPa, respectively. Fractography was employed to investigate the large scatter in fracture strengths and correlate fracture strength with fracture toughness through the size of the fracture origins.