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Microstructural effects on the mechanical behavior of B-modified Ti–6Al–4V alloys

Sen, Indrani and Tamirisakandala, S and Miracle, DB and Ramamurty, U (2007) Microstructural effects on the mechanical behavior of B-modified Ti–6Al–4V alloys. In: Acta Materialia, 55 (15). 4983 -4993.

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Small additions of B $(\leq0.4 wt.\%)$ to Ti alloys refine the as-cast microstructure significantly and improve the alloys’ mechanical performance. In this work, tensile, fracture and fatigue properties of the as-cast and hot isostatically pressed Ti–6Al–4V alloy with 0, 0.05, 0.10 and 0.40 wt.% B additions have been examined, with particular emphasis on identifying the microstructural length scale (grain size vs. lath size) that controls the mechanical properties of these alloys. Microstructural observations indicate an order of magnitude reduction in the prior \beta grain size, d, as well as a significant reduction in the \alpha lath size, \lambda, with B additions. It was observed that d and \lambda are correlated. With the refinement in the microstructure, the yield and ultimate tensile strengths, $\sigma_y$ and $\sigma_u$ respectively, increase whereas the fracture toughness, $K_{IC}$, decreases. Application of the Rice–Knott–Ritchie model for quasi-brittle cleavage fracture indicates that the reduction in $K_{IC}$, with increasing B content is due primarily to the reduced \lambda. Fatigue crack growth measurements show a gradual reduction in the threshold for fatigue crack propagation with $\sigma_y \sqrt\lambda$ dependence.

Item Type: Journal Article
Publication: Acta Materialia
Publisher: Elsevier
Additional Information: Copyright of this article belongs to Elsevier.
Keywords: Titanium alloys;Microstructure;Mechanical properties;Fracture toughness;Fatigue
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 18 Jul 2008
Last Modified: 19 Sep 2010 04:47
URI: http://eprints.iisc.ac.in/id/eprint/15102

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