5083アルミニウム合金のΔK_<th>近傍・疲労き裂進展特性と時効の影響

概要

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To understand the effects of aging on the near-threshold fatigue crack growth of a 5083-0 aluminum alloy, experimental analyses were conducted at 20℃, 80℃ and 130℃. The yield strength and the ultimate strength were both unchanged after aging at 80℃ and 130℃ for 6 000 hours. The 130℃ aging, however, induced an increase of electical conductivity, a decrease of impact value and a change of da/dn vs ΔK relations, except for the value of ΔK_<th> itself. The 80℃ aging did not affect the above properties. Crystallographic facets were found near the ΔK_<th> in samples, but the distrbution pattern differed between the virgin and the 130℃ aged ones. Grain boundary cracking was also observed in the 130℃ aged ones, bening perpendicular to the main fracture surface. Irrespective of temperature and aging treatment, the cyclic plastic zone size at the crack tip was 13〜19μm, comparable to the grain size, at the onset of crystallographic facets, and was 2〜2.1μm at the ΔK_<th>.
1986-12-25