Effect of Cu coating on interfacial behavior of Csf-Cu/AZ91D composites: Wettability and crack propagation mechanism

Short carbon fibers (Csf) are modified with Cu coating to improve interfacial behavior including wettability and crack propagation of the Csf/AZ91D composites. Wetting angle tests and in-situ tensile tests are direct approaches to characterize interfacial behavior. XPS spectra reveal that the Cu coating can increase the content of Cu element and CO bond, which improves the surface free energy of the Csf by 144.8%. Wetting angle tests suggest that the Cu coating can decrease the contact angle of molten AZ91D on Csf from 127° to 44°. In-situ SEM images show that for Csf/AZ91D composites, most of the cracks can directly cut off the Csf owning to the stress concentration at the interface. After the Cu coating modified Csf, the reduction of Al4C3 at the interface can release the stress concentration at the interface and protect the Csf from adverse interfacial reactions, significantly improving the ultimate tensile strength (UTS) of the composites by approximately 48.7%.