Ti-13V-11Cr-3Al合金の疲労き裂伝ぱ挙動に及ぼす水素チャージの影響

抄録

In order to investigate the influence of hydrogen on the fatigue crack propagation behavior of β-titanium alloy, two types of fatigue tests were carried out. One was the fatigue test in air on the hydrogen-precharged specimens, where the charging was carried out in H₂SO₄ aqueous solution electrolytically under the current density i_c of 1000A/m² for 260ks. Another was the fatigue test under electrolytic hydrogen-charging in H₂SO₄ aqueous solution at i_c=1000 or 3000A/m². Both test results were compared with the result obtained from the fatigue test of the non-charged specimen in air.
The fatigue crack propagation rate da/dN of the precharged specimen was much larger than the da/dN of the non-charged specimen in all the range of stress intensity factor, ΔK. The crack propagation rate da/dN under hydrogen charging was larger than the da/dN of the non-charged specimen only when ΔK was smaller than 15MPa·m^1/2, and the da/dN was much smaller than that of the precharged specimen. The fatigue fracture surface of the specimens which were hydrogen-charged by both methods revealed the cleavage fracture, which corresponded to the decrease in cohesive strength of the cleavage plane of β-phase by the dissolution of hydrogen atoms.