Microstructure and mechanical properties of Ti-6Al-4V/316L dissimilar materials with FeCrCuV medium-entropy alloy transition layer by laser metal deposition

Abstract

To avoid brittle intermetallic compounds during direct connection of the Ti-6Al-4V alloy and 316L stainless steel, the FeCrCuV medium entropy alloy (MEA) is designed as the transition layer, and the 316L/FeCrCuV/Ti-6Al-4V dissimilar materials are fabricated by laser metal deposition (LMD). The heterogeneous interfaces of 316L/FeCrCuV and FeCrCuV/Ti-6Al-4V are investigated by a scanning electron microscope (SEM), an energy dispersive spectroscope, and electron backscatter diffraction. The results indicate that common brittle intermetallic compounds TiFe and TiFe2 at Ti-6Al-4V/316L heterogeneous interfaces disappear, and the BCC/FCC dual-phase solid solution structure is obtained due to the solid solution effect of the FeCrCuV transition layer. Refined grains appear at heterogeneous interfaces of 316L/FeCrCuV and FeCrCuV/Ti-6Al-4V for the rapid cooling rate during LMD, which results in fine grain strengthening. The microhardness near heterogeneous interfaces increases the solution strength and fine grain strengthening. Furthermore, the design of the FeCrCuV transition layer with a dual-phase structure improves the coordinated deformation ability of 316L/FeCrCuV/Ti-6Al-4V and results in higher tensile strength.