Eliminating microstructure and mechanical anisotropy of Ti-6.5Al-2Zr-1Mo-1 V manufactured by hot-wire arc additive manufacturing through boron addition

Hot-wire arc additive manufacturing (HWAAM) raises new opportunities to fabricate large-scale integral titanium components due to its high deposition rate. However, microstructural heterogeneity and mechanical anisotropy are critical issues for the wide application of HWAAM. This study took Ti-6.5Al-2Zr-1Mo-1V as an example to demonstrate that these two issues can be alleviated through tuning the alloy composition. Boron addition (0.1wt.%) led to the formation of TiB whiskers, and most of the whiskers densely clustered along the β grain boundaries. Boron addition was effective in the β grain refinement and texture weakening, which contributed to the reduction of α phase heterogeneity. The mechanical anisotropy was significantly reduced because of the elimination of the microstructural heterogeneity, especially the elimination of the coarse columnar β grains and the continuous grain boundary α phase. The tensile properties of the boron modified part were slightly poorer than that of the unmodified part, because the separation of the TiB aggregates led to the premature failure of the modified part. Graphical abstract