Phase Field Simulations of Autocatalytic Formation of Alpha Lamellar Colonies in Ti-6Al-4V

We present phase field simulations incorporating contributions due to chemical free energy, anisotropic interfacial energy, and elastic energy due to transformation strain, to demonstrate the nucleation and growth of multiple variants of alpha from undercooled beta in Ti-6Al-4V under isothermal cond...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2016-12, Vol.47 (12), p.6577-6592
Main Authors: Radhakrishnan, Bala, Gorti, Sarma, Babu, Suresh Sudharsanam
Format: Article
Language:English
Subjects:
additive manufacturing
basket-weave
Characterization and Evaluation of Materials
Chemistry and Materials Science
Colonies
colony
Composite materials
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Crystallography
Energy
Materials Science
Metallic Materials
Nanotechnology
Nucleation
Nuclei
phase field
Physical metallurgy
Simulation
Strain
Structural Materials
Surfaces and Interfaces
Thin Films
Titanium base alloys
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Summary:We present phase field simulations incorporating contributions due to chemical free energy, anisotropic interfacial energy, and elastic energy due to transformation strain, to demonstrate the nucleation and growth of multiple variants of alpha from undercooled beta in Ti-6Al-4V under isothermal conditions. A new composite nucleation seeding approach is used within the phase field simulations to demonstrate that the presence of a pre-existing strain field can cause the nucleation of specific crystallographic variants of alpha based on minimization of local elastic strain energy. Under conditions where specific combinations of elastic strains exist, for example in the vicinity of one or more pre-existing alpha variants, the nucleation of a new alpha variant is followed by the successive nucleation of the same variant in the form of a lamellar colony by an autocatalytic mechanism. At a given thermodynamic undercooling, the colony structure was favored at a nucleation rate that was low enough to allow sufficient growth of previously nucleated variants before another nucleus formed in their vicinity. Basket weave morphology was formed at higher nucleation rates where multiple nuclei variants grew almost simultaneously under evolving strain fields of several adjacent nuclei.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-016-3746-6