Effect of the Beam Current during the Electron-Beam Melting of Titanium Alloy Ti–6Al–4V on the Structural Features and Phase Transitions in Gas-Phase Hydrogenation

Resumo

The structure of the titanium alloy Ti–6Al–4V manufactured by electron-beam melting is shown to be represented by initial β-phase grains more than 40 μm in size; the internal volume of the grains is filled with α-phase precipitates in the form of plates. The average size of the α plates is 1.6, 2, and 5 μm at beam currents of 2, 2.5, and 3 mA, respectively. In situ X-ray diffractometry using synchrotron radiation shows that the phase transitions in the titanium alloy are divided into three main stages during hydrogenation to a concentration of 0.6 wt % at a temperature of 650°C and a pressure of 1 atm. An increase in the beam current from 2 to 3 mA does not significantly affect the phase composition of the alloy. During hydrogenation, the growth rate of the volume concentration of the β phase is lower at a higher beam current. This indicates a decrease in the rate of hydrogen absorption with increasing beam current, which is associated with an increase in the size of α plates.