Ti-6Al-4V/SUS316L dissimilar joints with ultrahigh joint efficiency fabricated by a novel pressure-controlled joule heat forge welding method

Abstract

Ti-6Al-4V/SUS316L dissimilar joints were manufactured by a novel solid-state joining method named “pressure-controlled joule heat forge welding”. The microstructure and mechanical properties of the joints were systematically investigated. Both materials were homogeneously deformed by applying the pressure corresponding to the intersectional point of the temperature-dependent yield strength. Along the joint interface, the uniform hardness distributions in the center and periphery regions were obtained because the heat input generated by the joule heat was homogeneous from center to periphery. The welding temperature was able to be decreased to suppress the formation of the intermetallic compound (IMC) layers by applying the high pressure because the welding is accompanied and accomplished by the interfacial deformation and the high pressure affects the deformable temperature. As a result, when the applied pressure was increased from 300 MPa to 450 MPa, the width of the IMC layers was decreased to around 28 nm. As the upset increased, the interfacial area ratio to base material increased hence the interfacial defects were successfully suppressed, and the tensile strength increased by removing the ragged surface and the oxide layers existing on the surface of the base material. Eventually, the joint efficiency reached 98.5 % compared to the base material.