Interfacial microstructure and strengthening mechanisms of C_f/Mg composite with double-layer interface

In order to overcome the interfacial incompatibility of carbon fiber reinforced magnesium matrix (C_f/Mg) composites, a double-layer interface (ZrO₂–MgO) is designed in this work. Carbon fiber was modified with ZrO₂ coating by sol-gel process. Microstructural examination reveals that MgO layer forms on the surface of ZrO₂ coating by ZrO₂ reacting with Mg during the composite fabrication. Such double-layer interface could inhibit Al₄C₃ and hence prevent fiber damage. Meanwhile, the wettability was improved for the reaction between ZrO₂ and Mg. Thus the tensile strength of ZrO₂-C_f/AZ91D composite was 68.0% higher than that of the unmodified one. Due to the fiber bundle pull-out, debonding and crack deflection, the toughness of C_f/Mg composite with double-layer interface is increased simultaneously.