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Open AccessFeature PaperArticle

Effect of TiB Orientation on Near-Threshold Fatigue Crack Propagation in TiB-Reinforced Ti-3Al-2.5V Matrix Composites Treated with Heat Extrusion

1
Department of Mechanical Engineering, Faculty of Engineering, Shizuoka University, Shizuoka 422-8017, Japan
2
Department of Mechanical Engineering, Kobe University, Kobe, Hyogo 657-8501, Japan
3
Department of Materials Processing, Graduate School of Engineering, Tohoku University, Miyagi 980-8577, Japan
4
Ariane Group, 78130 Les Mureaux, France
*
Author to whom correspondence should be addressed.
Materials 2019, 12(22), 3685; https://doi.org/10.3390/ma12223685 (registering DOI)
Received: 2 October 2019 / Revised: 6 November 2019 / Accepted: 7 November 2019 / Published: 8 November 2019
(This article belongs to the Special Issue Metal Matrix Composites: Experimental and Simulation)
TiB-reinforced Ti-3Al-2.5V matrix composites, in which TiB whiskers are oriented parallel to the direction of heat extrusion, were fabricated via mechanical alloying and hot isostatic pressing (HIP). To investigate the near-threshold fatigue crack propagation in TiB-reinforced Ti-3Al-2.5V matrix composites, stress intensity factor K-decreasing tests were conducted for disk-shaped compact specimens having two different orientations of TiB whiskers at force ratios from 0.1 to 0.8 under ambient conditions. The crack growth rates, da/dN, for the composites incorporating TiB whiskers oriented perpendicular to the direction of crack growth were constantly lower than those obtained in the case where the orientation was parallel at the same stress intensity range ΔK, while the threshold stress intensity range, ΔKth, was higher. This effect can be explained by the increase in the degree of roughness-induced crack closure resulting from the perpendicular TiB, because fatigue cracks preferentially propagated across the boundaries between the matrix and the TiB in certain regions. In contrast, the effective threshold stress intensity range, ΔKeff,th, for composites was unaffected by the TiB orientation at low force ratios. View Full-Text
Keywords: fatigue; fracture mechanics; titanium alloy; titanium boride; crack closure fatigue; fracture mechanics; titanium alloy; titanium boride; crack closure
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Kikuchi, S.; Tamai, S.; Kawai, T.; Nakai, Y.; Kurita, H.; Gourdet, S. Effect of TiB Orientation on Near-Threshold Fatigue Crack Propagation in TiB-Reinforced Ti-3Al-2.5V Matrix Composites Treated with Heat Extrusion. Materials 2019, 12, 3685.

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