In situ synthesis of a gamma-Al2O3 whisker reinforced aluminium matrix composite by cold pressing and sintering

An aluminium matrix composite reinforced by in situ-generated gamma-Al2O3 whiskers was fabricated from a simple Al-H3BO3 system through cold pressing and sintering. The gamma-Al2O3 whiskers with an average diameter of 20 nm and an aspect ratio of 10-15 were synthesized during the sintering process and homogeneously distributed in the Al matrix. As a result of the perfect lattice matching between gamma-Al2O3 and the Al matrix, the gamma-Al2O3 whisker is a desired reinforcement for the Al matrix, improving the ultimate tensile strength and hardness to 217 MPa and 43.5 HV, respectively, with a satisfactory ductility of 11%. Differential scanning calorimetry analysis shows that the growth of the whisker occurred at 550-650 °C, and the ball milling energy has a significant effect on whisker growth.