Role of metal surface amorphization on enhancing interfacial bonding in TC4-UHMWPE hybrid structure

Securing high-performance bonding between metals and non-polar polymers presents a significant challenge. Existing research mainly focused on the metal surface treatments to modify the morphology and chemical components, or introducing polar groups on the non-polar polymer via complicated modifications. This study introduced a novel interface engineering strategy involving metal surface amorphization, aimed at producing a high-performance hybrid structure of Ti6Al4V titanium alloy (TC4) and ultra-high molecular weight polyethylene (UHMWPE) for applications in artificial joint prostheses. The amorphous oxide layer grown on the TC4 surface significantly enhanced its chemical reactivity, facilitating interfacial chemical bonding between TC4 and in-situ functionalized UHMWPE during thermal-direct bonding. High-performance TC4-UHMWPE hybrid structures with lap-shear strength reaching 17.77 MPa (lap-shear force of 3732.4 N) were obtained using friction spot joining, underscoring the effectiveness of chemical bonding as the primary interfacial bonding mechanism. Meanwhile, both the chemical bonding type and the reaction mechanism were revealed with solid experimental evidence and density functional theory calculations for the first time. More importantly, the differences in bonding characteristics between amorphous and crystalline titanium oxides were revealed. This research not only deepens the understanding of interfacial bonding mechanisms and behaviors between different titanium oxides and polar groups but also provides a pioneering insight into manufacturing high-performance metal-polymer hybrid structures.