Interfacial Reactions in the Bonding Zones of Explosively Welded Tantalum to Stainless Steel Sheets

Abstract

The microstructure of the interfacial layers of explosively welded Ta/stainless steel (SS) and Ta/Cu/SS composites is investigated by X-ray synchrotron radiation, scanning (SEM), and transmission (TEM) electron microscopies. SEM analyses show that all interfaces between joined sheets undergo wave-shaped deformation with the solidified melt regions situated preferentially in the wave vortexes and at the wave crests. These reaction regions show a nonuniform distribution of phases in terms of chemical composition with elements belonging to both neighboring sheets. According to TEM analyses and synchrotron X-ray measurements, the solidified melt regions between Ta and SS predominantly consist of brittle, amorphous, or nanocrystalline phases that are not observed in equilibrium phase diagrams. The microstructure of the solidified melt near the Ta/Cu interface is dominated by Cu and Ta nanoparticles and small dendrites, typically less than 100 nm in diameter, whereas nanosized crystalline phases with complex chemical compositions are identified near the Cu/SS interface.