Experimental investigation and molecular simulation on the chemical bonding between laser-treated titanium alloy amorphous surface and epoxy adhesive

Laser surface modification is employed to enhance the interfacial bonding performance of metal-adhesive structures, and chemical bonding plays a crucial role in achieving strong interfacial adhesion. Understanding the mechanism of interfacial chemical bonding between laser-treated metal surface and adhesive at the molecular/atomic scale is key to further optimizing the interfacial bonding performance. In this study, the morphology and chemical composition of laser-induced amorphous titanium oxide on titanium alloy surfaces, as well as its enhanced effect on interfacial bonding performance, were characterized using scanning electron microscopy, energy dispersive spectroscopy, and single lap-shear testing.Through X – ray photoelectron spectroscopy analysis, experimental evidence is provided for the formation of Ti-O-C chemical bonds between the amorphous titanium oxide and adhesive. Transmission electron microscopy observations and molecular dynamics simulations reveal that the strong non-bonding intereactions between amorphous titanium oxide and adhesive enables the adhesive molecules to fully infiltrate the amorphous titanium oxide, providing more sites for chemical bond formation. Density functional theory calculations demonstrate that Ti-O-C chemical bonds tend to form between the dissociated hydroxyl group of the adhesive and titanium oxide, facilitated by a relatively low reaction barrier. This chemical bonding promote the formation of a strong bonding structure at the adhesive interface.