Fine structure of coated whiskers in Al(18)B(4)O(33)w/gamma-Al2O3/6061Al composite

Sol-gel gamma -Al2O3 coating was deposited onto surfaces of aluminum borate whiskers to control the spinel reactions between whiskers and matrix alloy s. High-resolution electron microscopy (HREM) observations of the whisker d efects and coating structure in the squeeze-cast Al(18)B(4)O(33)w/gamma -Al 2O3/6061Al composite were carried out. Stacking faults and edge dislocation s in the whiskers were directly observed, and zigzag anti-phase boundaries were also found. A deformation of whiskers along sectional direction was ob served, which was determined to be a source of in situ fracture of whiskers . The sol-gel gamma -Al2O3 coating was a nanocrystalline material with an a verage grain size of 5 nm. (C) 2001 Kluwer Academic Publishers.