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Title: Phase field simulations of autocatalytic formation of alpha lamellar colonies in Ti-6Al-4V

Here, we present phase field simulations incorporating energy contributions due to thermodynamics, and anisotropic interfacial and strain energies, to demonstrate the nucleation and growth of multiple variants of alpha from beta in Ti-6Al-4V under isothermal conditions. The simulations focused on the effect of thermodynamic driving force and nucleation rate on the morphology of the transformed alpha assuming that the partitioning of V between beta and alpha is negligible for short isothermal holds. The results indicate that a high nucleation rate favors the formation of the basket-weave structure. However, at a lower nucleation rate the simulations show the intragranular nucleation of a colony structure by an autocatalytic nucleation mechanism adjacent to a pre-existing alpha variant. New side-plates of the same variant appear to nucleate progressively and grow to form the colony. The isothermal simulation results are used to offer a possible explanation for the transition from a largely basket weave structure to a colony structure inside narrow layer bands occurring during continuous heating and cooling conditions encountered during laser additive manufacturing of Ti-6Al-4V.
Authors:
 [1] ;  [1] ;  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 47; Journal Issue: 12; Journal ID: ISSN 1073-5623
Publisher:
ASM International
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; phase field; basket-weave; colony; additive manufacturing
OSTI Identifier:
1327583