PROCESSING OF HYBRID STRUCTURES CONSISTING OF Al-BASED METAL MATRIX COMPOSITES(MMCs)WITH METALLIC REINFORCEMENT OF STEEL OR TITANIUM

摘要

Paniculate reinforced, Al-based metal matrix composites(MMCs)offer many advantages as engineering materials, including low density relative to titanium and steel- based metals, high specific stiffness, high specific strength, tailorable coefficient of thermal expansion(CTE), and high wear resistance. However, these materials have low toughness and elongation relative to pure structural metals due to the presence of the brittle ceramic particles within the aluminum matrix. The present work aims to resolve the low elongation weakness of Al-based MMCs by incorporating metallic "macro-reinforcement" into the material, forming a hybrid structure. Example hybrid configurations are Al-based MMCs with an internal network of steel or titanium rebar, or Al-based MMCs cast into a steel or titanium grid structure. With proper selection of the MMC formulation, its CTE can be matched to that of the metallic macro-reinforcement, leading to a stress-free structure. Alternatively, the CTEs can be tailored such that the metallic macro-reinforcement applies a compressive residual stress to the MMC, thus providing enhanced mechanical response. Specifically, the work describes processing of MMC-metal hybrid structures, examines interfacial microstructures, and assesses failure behavior.