日本金属学会誌

J. Japan Inst. Metals, Vol. 52, No. 11 (1988),
pp. 1057-1062

Effect of Primary α Phase on Fatigue Crack Growth of Ti-6Al-4V Alloy

Akira Nozue1 and Tadatsune Okubo1

1Department of Mechanical Engineering, Faculty of Science and Technology, Sophia University, Tokyo

Abstract:

The purpose of the present paper is to clarify fatigue crack growth behavior in Ti-6Al-4V alloy consisting of primary α and matrix. The phase ratio of the primary α to the matrix was varied from about 65 to 20% with the solution treatment. The temperature range for this treatment was between 1148 and 1228 K. Fatigue tests were carried out in the Δ K region from the fatigue threshold to the critical fatigue fracture under constant load amplitude with CT specimens of 6 mm thickness. The crack propagated preferentially in the primary α phase compared with the matrix. On the fracture surfaces of the primary α phases, comparatively flat facets were observed in the low Δ K region and the striations were clearly observed in the high Δ K region. In addition, martensite boundary cracks existed in the matrix. It was found that the primary α fraction mainly controlled the fatigue crack growth rate in the region of the stable crack growth.


(Received 1988/3/23)

Keywords:

fatigue, crack propagation, microscopic striation, primary alpha phase, facet, fractography, titanium-6% aluminum-4% vanadium alloy


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