Interfacial reactions and mechanical properties of 6061A1 matrix composites reinforced with alumina-coated Al18B4O33 whiskers

Sol-gel gamma-Al2O3 and alpha-Al2O3 ceramic coatings were deposited onto surfaces of aluminum borate whiskers to control the spinel reactions between whiskers and matrix alloys. Interface observations, tensile experiments and hardness measurements of the composites were conducted to evaluate the coating effect. By comparison with gamma-Al2O3 coating, the alpha-Al2O3 coating was found to be more effective in controlling the interfacial reactions, and it helped to enhance the elastic modulus of the composite. The introduction of alumina coatings to the composite postponed the peak-aging process, due to a smaller depletion of magnesium in the matrix of the coated composites. (C) 2000 Elsevier Science B.V. All rights reserved.