Ti6Al4V/SS316 multi-metallic structure fabricated by laser 3D printing and thermodynamic modeling prediction

Directly, welding titanium alloy and stainless steel can cause brittle Ti-Fe intermetallics which compromise join bonds' mechanical properties. In this research, laser 3D printing was applied to explore a new Ti6Al4V/SS316 multi-metallic structure, in which a novel filler transition route was introduced (Ti6Al4V a V a Cr a Fe a SS316) to eliminate the Ti-Fe intermetallic phases. To evaluate this novel route, a thin wall sample was fabricated via laser 3D printing following the transition route. Microstructure characterization and composition distribution analysis were performed via scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). The SEM depicted the microstructure morphology. The EDS result showed element gradient distribution, which reflected the transition route design. X-ray diffraction (XRD) tests indicated formed stable phases in the sample. The formed phase at Cr/Fe interface was also tested through analyzing microstructure and XRD pattern, then compared with the standard sigma phase XRD pattern. All of the above results demonstrated that the intermetallics were effectively eliminated by using the transition route. In addition, a thermodynamic modeling was employed to predict the Ti6Al4V/SS316 multi-metallic structure's formed phases at room temperature. All the predicted stable phases were verified by the XRD results. The above research results are good contributions in the research of joining titanium alloy and stainless steel.