α+β型Ti-6Al-4V合金の水素化物の析出挙動

Abstract

The behavior of hydrogen absorption and hydride precipitation has been studied on a Ti-6Al-4V alloy cathodically charged at various current densities using X-ray diffraction analysis, internal friction measurement and transmission electron microscopy.The 200 spacing and considerable X-ray line broadening of β phase increased with increasing cathodic charging time. The α phase, however, was not significantly affected by the cathodic charging.A relaxation peak relating to the hydrogen atoms in the β phase was observed in the internal friction versus temperature curve. The increase in the peak height corresponded to the increase in the 200 spacing of β phase in the X-ray line profile.Hydrogen atoms in the β phase were detected by both the internal friction measurement and X-ray diffraction analysis. It was observed that the hydrides mainly precipitated at the α/β interface for cathodic charging of the low current density, but precipitated in both the α phase and the β phase for the high current density.The precipitation amount of hydrides estimated from the X-ray line profile and the peak height at 190-220 K in the internal friction versus temperature curve increased with increasing charging time for the high current density. Consequently, the peak was considered to be related to the hydrides. The hydrides were detected by internal friction, though it was difficult to detect the hydrides by using X-ray diffraction analysis for the low current density.