Hydrogen influence on defect structure and mechanical properties of EBM Ti-6Al-4V

Abstract

Abstract The defect structure and mechanical properties of the samples manufactured from Ti-6Al-4V powder by electron beam melting (EBM) before and after hydrogenation was studied. It has been established that hydrogenation of EBM titanium alloy to a concentration of 470\u202fppm leads to the formation of titanium γ-hydride, the volume content of which is 2.2%. A further increase in the concentration of hydrogen to 650\u202fppm is accompanied by a slight increase in the content of the hydride phase, while the proportion of the β phase of titanium increases (to 4.9%). When the hydrogen content is 900\u202fppm, the fraction of γ hydride decreases and the fraction of the beta phase decreases to 4.2%, and the formation of the hydride phase δ is observed. The introduction of hydrogen leads to a decrease in the wear and an increase in the hardness of EBM Ti-6Al-4V samples. This circumstance is due to the microstructure refinement under the action of hydrogen and the formation of secondary phase precipitates. The hydrogen content increases, the dislocation density and the concentration of hydrogen-vacancy complexes linearly increase, which indicates that hydrogen not only actively interacts with existing defects but also induces the formation of new defects.