Nanoindentation Investigation of Ti/Fe Bimetallic Plate Welded by Vanadium Filler
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This article presents a systematic investigation of microstructures and mechanical properties of Ti/Fe bimetallic plates butt welded using vanadium (V) filler. It is found that the Ti/V/Fe interface is featured by dendrite structures consisting of β-Ti, FeTi, Fe2Ti, and α-Ti phases, with a hardness ranging from 5.5 to 16.25 GPa. V weld metal (WM) mainly consists of V solid solution phase with some α-Ti precipitating along the grain boundaries. A series of intermetallics, e.g., σ-FeV and Fe2Ti, are formed at the V/Fe WM interface. V WM has relatively uniform hardness (2 to 5 GPa), but hardness fluctuation is observed at the V/Fe WM interface, from 2 to 16.3 GPa. Cracks tend to initiate and propagate along the regions rich in σ-FeV and Fe2Ti. The reheated zone (V/Fe WM) by subsequent welding passes may promote the formation of σ-FeV, responsible for the cracking. Based on the Fe-Ti-V ternary phase diagram, a schematic model is established to predict the phase transformation in these welds.
This work was supported by the Startup Fund for Doctors of Xi’an University of Technology (Grant No. 101-451118006), Australian Research Council Discovery Project (Grant No. DP180101955), and National Natural Science Foundation of China (Grant No. 51575251). The data reported in this article were obtained at the Central Analytical Research Facility (CARF) with the technical assistance of Mr. Tony Raftery and Dr. Dilini G.D. Galpaya, Institute for Future Environments (QUT).