Solid-state interfacial reaction and load transfer efficiency in carbon nanotubes (CNTs)-reinforced aluminum matrix composites

Carbon nanotubes (CNTs)/aluminum (Al) composites with various interfacial reaction degrees were fabricated by powder metallurgy at sintering temperature range of 700–900 K (75–96% melting point of Al). Interfacial reaction product, aluminum carbide (Al₄C₃), was formed in Al matrix composites (AMCs) reinforced by homogeneously-dispersed CNTs. Microscopy observations revealed three types of temperature-dependent interfaces, i) clean CNT-Al interfaces without interfacial carbide, ii) CNT-Al₄C₃-Al interfaces for partially reacted CNTs with Al₄C₃ nanoparticles, and iii) Al₄C₃-Al interface for in-situ Al₄C₃ nanorods evolved from completely reacted CNTs. Interfacial Al₄C₃ on partially reacted CNTs led to significant improvement of interfacial strength and consequent enhancement of load transfer efficiency in AMCs, compared to those composites without carbide. The load transfer mechanism of CNTs in composites was confirmed by the pull-out phenomena during in-situ tensile tests. The role of interfacial carbide played in determining the load transfer efficiency of CNTs was discussed. This study may provide new insights into the interfacial phenomena and load transfer mechanism in CNT-reinforced metal matrix composites.