Microstructural characterization and mechanical properties of microplasma oxidized TiO2/Ti joints soldered using Sn3.5Ag4Ti(Ce) active filler

Abstract

In this study, a micro-porous titania (TiO2) layer was synthesized on commercial pure Ti using the microplasma oxidation (MPO) method. Ti/Ti, MPO-TiO2 (MPO-Ti)/Ti and MPO-Ti/MPO-Ti were successfully active soldered using this Sn3.5Ag4Ti(Ce) active filler metal at 250 °C for 60 s. The microstructure and mechanical properties of the active soldered joints were investigated. Results indicate that trace Ce reacts with the MPO-Ti layer to form both CeO2 and Ti, corresponding to the reaction between Ti and Sn to form Ti6Sn5, and nano-sizes Ag3Sn phases adsorb at the active filler/MPO-Ti interfaces. Shear strength of soldered Ti/Ti, MPO-Ti/Ti, and MPO-Ti/MPO-Ti specimens were measured to be 16.3 ± 1.39, 11.3 ± 1.56, and 9.5 ± 1.24 MPa, respectively. The fracture of Ti/Ti specimen was found to produce along the Ti2Sn3 and solder matrix. In the MPO-Ti/MPO-Ti specimen, the fractures occurred through the active filler/MPO-Ti interface. In the MPO-Ti/Ti specimen, the fracture failure mode transferred from MPO layer/Ti interfacial fracture to fracture within the active filler.