ZnO- and ZnAl2O4-coated aluminum borate whiskers reinforced pure aluminum composites were fabricated by squeeze casting. The tensile properties of the composites at elevated temperatures were tested. The results indicate that the maximum tensile stress of the composite decreases with the increase of tensile temperature; however, the tensile strain of the composite initially increases and later declines. ZnO, especially, ZnAl2O4 coating of the whiskers can effectively improve the ultimate tensile strength of the composite at elevated temperatures. On the basis of fractographic analysis, the fracture mechanisms of the composites at elevated temperatures were also investigated.
ZnAl 2 O 4 -coated aluminum borate whiskers reinforced 2024Al composite was fabricated by squeeze casting. Interfacial microstructures and tensile properties of the composite were investigated. The results show that ZnAl 2 O 4 coating of the whiskers can improve the wettability of the whiskers by molten aluminum during squeeze casting, resulting in the increase of tensile properties of the composite. During thermal exposure, ZnAl 2 O 4 at the interface can effectively hinder harmful interfacial reactions, resulting in the improvement of thermal stability of the composite at high temperatures. Fracture mechanisms of the composite in as-cast and after thermal exposure were also investigated.
Pure aluminum composites reinforced by ZnAl2O4-coated aluminum borate whiskers were fabricated by a squeezing cast technique. Interfacial microstructures of the composites were observed using a transmission electron microscope (TEM). Thermal expansion behaviors of the composites were investigated in the range from 50 to 400°C. Effects of heat-treatment and thermal cycling on the thermal expansion behaviors of the composite were also investigated. The results show that the coefficient of thermal expansion (CTE) of the composites significantly decreases with the coating contents increasing. The average CTE of the composites further decreases after heat-treatment or thermal cycling.
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