GS04 高量度中における7075-T6押出材の疲労き裂伝ぱ特性

抄録

Effect of humidity on the growth properties of a fatigue crack in an age-hardened Al alloy was investigated in relative humidity of 25% and 85% at loading frequencies of 50 and 6Hz. Macroscopic growth mode of a crack was a tensile one in low humidity, while the mode changed from the shear one to the tensile one with increase in fatigue life in high humidity. The crack in low humidity propagated by forming striation. On the other hand, in high humidity, most of fracture surface was occupied by many slip planes in the shear mode crack, and many granular facets in addition to striations were observed in the tensile mode growth. The difference in growth mechanism was explained by microstructure and cyclic softening behavior of the alloy and hydrogen content.