Microstructure, wettability, and mechanical properties of ADC12 alloy reinforced with TiO2-coated carbon nanotubes

Aluminum matrix composites (AMCs) reinforced by CNTs as lightweight structural materials gain extensive attention. However, the crucial issue limited its application breadth is the poor interfacial bonding between the matrix and CNTs. In this paper, novel TiO2 nanoparticles-coated CNTs (TiO2 @CNTs) fabricated by the alcohol-thermal method were used as the reinforcement to prepare AMCs via high-intensity ultrasonic-assisted casting. The microstructure, wettability, interfacial bonding, and mechanical properties of TiO2 @CNTs/ADC12 composites were investigated in detail. By incorporating TiO2 nanoparticles on the surface of CNTs, the contact angle was reduced from 140.5° to 119°, indicating a significant improvement in the wettability of CNTs to aluminum melt. TEM results revealed that TiO2 nanoparticles homogenously dispersed on the surface of CNTs acted as an interlayer structure between CNTs and matrix, locking the CNTs and improving the CNTs-Al interfacial bonding. The semi-coherent interface was formed at the TiO2/α-Al interface, and the mismatch of (001)TiO2//(100)Al is only 6.52%, indicating a good lattice space matching between TiO2 and α-Al matrix. The TiO2 @CNTs/ADC12 composite with 1.2 wt% TiO2 @CNTs displayed high mechanical properties with yield strength and ultimate tensile strength of 196 MPa and 262 MPa, which were 54% and 29% higher than those of the matrix (127 MPa and 203 MPa), respectively. The better mechanical properties may be attributed to good interfacial bonding caused by the semi-coherent interface created by the TiO2 interlayer, leading to an effective load transfer from matrix to CNTs.