Ti-6Al-4V の低応力拡大係数域における大気中疲れき裂伝播特性の解析

概要

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Fatigue crack growth property in air in three kinds of Ti-6Al-4V was analyzed at stress intensity range less than 30kgf/mm^<3/2>. The following results were mainly obtained. 1) α phase shows cleavage-like fracture at low stress intensity range. The fracture mode of β phase depends on the shape of α precipitated in β phase. Fracture surface of β phase in which fine α particles precipitated is flat and featureless, and that in which lath like α plate formed is cleavage like. 2) Microstructure influences fatigue crack growth rate, which depends on the volume of α phase, shape of α particles in β phase etc. 3) ΔK threshold decreases with increase of stress ratio until more than 0.9. 4) The effective ΔK threshold is about 7.5kgf/mm^<3/2> without reference to microstructures, because the mode of fracture is intergranular at ΔK close to the ΔK threshold and is same among the three kinds of specimens.
社団法人日本鉄鋼協会の論文
1988-02-01