Mechanical properties of the alumina-coated Al18B4O33w/6061Al composites

To control the interfacial reactions in squeeze-casting aluminum borate whisker reinforced 6061Al composites, sol-gel γ- and α-Al2O3 coatings were deposited on the whisker surfaces for preparation of the alumina-coated composites. Tensile and bending tests of the coated and uncoated composites were carried out. Experimental results indicated that, although the room-temperature strength of the composite was not improved, the introduction of alumina coatings contributed to the enhancement of elastic modulus. To eliminate the strength-scattering effect and to evaluate the thermal-resistance of alumina coatings, an index of strength-decrease degree (Δσbd) was useful. The alumina coatings were found to improve the compositeʹs high-temperature strength and change the fracture mechanisms of the composite at different testing temperatures.