Ti-6Al-4V合金のき裂発生および初期き裂伝ぱ過程に及ぼすβ-STA熱処理の影響

概要

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To clarify the effects of β-STA processing on fatigue behaviors of Ti-6Al-4V alloy, microcrack initiation and propagation processes were successively observed in a series of rotating bending fatigue tests of β-STA material and annealed Ti-6Al-4V alloy. The main results obtained are as follows: (1) When the stress higher than a fatigue limit is repetitively applied to the specimen, microcracks appear from the α phase for the annealed material, while they appear along the fine acicular microstructure for the β-STA material. When the stress corresponding to a fatigue limit is repetitively applied to the specimen, no microcrack appears in either of the materials. Accordingly, the fatigue limit is determined by the microcrack initiation limit. (2) The fatigue limit of the β-STA material becomes about 30% higher than that of the annealed material. (3) In both materials, the equation dl/dN=Cσ^6l(C:constant, dl/dN:crack growth rate) holds, and constants C are nearly equal to each other. (4) The above conclusions (1), (2) and (3) mean that β-STA processing has little influence on resistance against the microcrack propagation but contributes to an increase in limiting stress for the microcrack initiation.
社団法人日本材料学会の論文
1994-04-15