日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 2 (1990),
pp. 153-160

Crack Growth Mechanism and Fracture Toughness in Extra Low Interstitials Grade Ti-6Al-4V Alloy

Shigemi Mashino1, Takao Horiya2, Hirowo G. Suzuki2 and Teruo Kishi3

1Engineering Research Laboratory, Japan Tobacco Inc., Hiratsuka
2R & D Laboratories-II, Nippon Steel Corporation, Sagamihara
3Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo

Abstract:

Three-dimensional location analysis and source characterization of acoustic emissions (AE) were conducted in the fracture toughness test to understand the microfracture process of Extra Low Interstitials (ELI) Ti-6Al-4V alloy with equiaxed α microstructure. scanning Electron Microscope observation was also carried out for both fracture surfaces and microstructures near the notch tips of the unloaded specimens to supplement the AE analysis.
From about 50% of the maximum load in the fracture toughness test of ELI Ti-6Al-4V, many microvoids with diameters smaller than 10 μm began to nucleate near the crack tip and then microcracks of about 20 to 40 μm in diameter were generated by coalescence of these microvoids. These microcracks were located about 30 to 50 μm above or below the fatigue pre-crack plane. The stress relaxation near the crack tip due to the microcracks and zigzag type coalesence of microcracks was thought to enhance the fracture toughness of ELI Ti-6Al-4V alloys.


(Received 1989/9/9)

Keywords:

fracture toughness, acoustic emission, source characterization, microcrack, stress relaxation, titanium-6 aluminium-4 vanadium alloy, extra low interstitials


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