Ti-6Al-4V合金の水素化物の析出挙動におよぼす金属組織の影響

Abstract

Effect of the microstructure on the hydride precipitation behavior has been studied on a Ti-6Al-4V alloy cathodically charged at various current densities using internal friction measurement and transmission electron microscopy.The hydride precipitation by cathodic charging was observed not only near the surface but also inside the specimen for the β annealed specimen consisting of α+β microstructure. The hydride precipitation was observed only near the surface of the specimen for the β quenched specimen of α′ microstructure, and for the α+β quenched specimen consisting of α+α′ microstructure. The γ hydride phase precipitated at the α⁄β interface and inside the α and β phases for the β annealed specimen. The γ phase also precipitated at the α⁄β or α′⁄α interface and inside the α′ phase for the α+β quenched specimen.An internal friction peak appearing at 190-220 K by using 1 Hz was related to hydride precipitation. The peak height increased with increasing cathodic charging time.The precipitation of hydrides caused the Bordoni peak related to the strain of α phase matrix. The peak at 220-280 K at 1 Hz appeared only with the presence of a large amount of hydrogen and strain, and the peak was considered to be due to the interaction of dislocation with hydrogen.The Bordoni peak and the peak at 220-280 K at 1 Hz appeared clearly for the α+β quenched specimen and the β quenched specimen. However, their peaks were difficult to occur for the β annealed specimen, because of the presence of β phase.