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-Al 2 O 3 whiskers was fabricated from a simple Al-H 3 BO 3 system through cold pressing and sintering. The gamma-Al 2 O 3 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-Al 2 O 3 and the Al matrix, the gamma-Al 2 O 3 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.