Tailoring the interface with the in-situ formed chromium oxide and carbide for higher mechanical properties of copper matrix composites

The weak interface is a key issue that needs to be addressed for the carbon nanotubes (CNTs) reinforced metal matrix composites. Herein, uniform and continuous Cr(OH)3 coating was firstly decorated on the surface of CNTs, and Cr(OH)3 coating was subsequently thermally decomposed into the Cr2O3 transition layer during the fabrication processes for the Cu matrix composite. It is found that the precoating Cr(OH)3 on CNTs can promote the dispersion of CNTs in the Cu matrix because the coating can reduce the density difference between CNTs and Cu powders. Meanwhile, the Cr2O3 transition layer has obvious constituent interaction with the Cu matrix, and in-situ nanosized Cr carbides (Cr2C3 and Cr23C6) form between the CNTs and Cr2O3 layer, forming a composite interface structure. Benefiting from the homogeneous dispersion of the decorated CNTs and enhanced interfacial bonding, the compression yield strength of the bulk composite reaches 383.5 & PLUSMN;21.0 MPa, showing a 217% and 147% increase over the pure Cu and the composite reinforced by uncoated CNTs, respectively. The substantially enhanced strength mainly derives from the strengthening mechanisms of Orowan looping and load transfer. The developed novel strategy paves a new route for interface regulation and strength improvement of other CNTs reinforced metal matrix composites.

Automated summary

In this study, a uniform and continuous Cr(OH)3 coating was decorated on the surface of carbon nanotubes (CNTs), which was subsequently decomposed into a Cr2O3 transition layer during the fabrication processes for the Cu matrix composite. Precoating Cr(OH)3 on CNTs can promote their dispersion in the Cu matrix and reduce the density difference between CNTs and Cu powders. The formed composite interface structure, with in-situ nanosized Cr carbides (Cr2C3 and Cr23C6), enhances the interfacial bonding and significantly improves the compression yield strength of the bulk composite.