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α phase growth and branching in titanium alloys

Shi, R and Choudhuri, D and Kashiwar, A and Dasari, S and Wang, Y and Banerjee, R and Banerjee, D (2021) α phase growth and branching in titanium alloys. In: Philosophical Magazine, 102 (5). 389 -412.

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Official URL: https://doi.org/10.1080/14786435.2021.1998693


The morphology and spatial distribution of alpha (α) precipitates have been mapped as a function of Mo content in Ti-Mo binary alloys employing a combinatorial approach. Heat-treatments were carried out on compositionally graded Ti-xMo samples processed using a rapid throughput laser engineered net shape (LENS) process. The composition space spans 1.5 at% to 6 at% Mo with ageing at 750°C, 650°C and 600°C following a β solution treatment. Three distinct regimes of α morphology and distribution were observed. These are colony-dominated microstructures originating from grain boundary α allotriomorphs, bundles of intragranular α laths, and homogeneously distributed individual fine-scale α laths. Branching of the α precipitates was observed in all these domains in a manner reminiscent of solid-state dendritic growth. The phenomenon is particularly apparent at low volume fractions of α. Similar features are present in a wide variety of alloy compositions. 3-dimensional features of such branched structures have been analysed. Simulation of the branching process by phase field methods incorporating anisotropy in the α/β interface energy and elasticity suggests that it can be initiated at growth ledges present at broad faces of the α laths, driven by the enhancement of the diffusion flux at these steps. The dependence of branching on various parameters such as supersaturation and diffusivity, and microstructural features like ledge height and distribution and the presence of adjacent α variants has been evaluated.

Item Type: Journal Article
Publication: Philosophical Magazine
Publisher: Taylor and Francis Ltd.
Additional Information: The copyright for this article belongs to the Taylor and Francis Ltd.
Keywords: Grain boundaries; Molybdenum alloys; Morphology; Phase transitions; Titanium alloys, 3d metallographies; Combinatorial approach; Composition space; Mo content; Net-shape; Phase field models; Phase growth; Solid state branching; Solution treatments; Titanium (alloys), Binary alloys
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 29 Dec 2021 06:35
Last Modified: 11 Jul 2022 06:01
URI: https://eprints.iisc.ac.in/id/eprint/70756

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