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Title: Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM)

Abstract

Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that fabricates parts by selectively scanning consecutive powder layers with an electron beam. Additive manufacturing technologies are increasing in importance for aerospace and medical applications, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. Ti-6Al-4V is the most widely used and studied alloy for this technology, and is the focus of this work in its Extra Low Interstitial (ELI) variation. The layered manufacturing of metallic components by EBM creates a unique directional microstructure, and consequently, anisotropic properties. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology’s potential extension to high-integrity applications. Here in this study, fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied for different stress ratios and crack growth stages. The interaction between the directional as-fabricated EBM microstructure and FCG was investigated and compared to that of the equiaxed β annealed microstructure obtained by annealing above themore » β transus temperature. Finally, the FCG threshold, ΔKth, was analytically modeled for the two relative crack propagation directions at different stress ratios, and FCG microstructural mechanisms were established for all three regions of crack propagation.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [2]; ORCiD logo [2]
  1. Worcester Polytechnic Inst., Worcester, MA (United States). Integrative Materials Design Center
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Manufacturing Demonstration Facility
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office
OSTI Identifier:
1394298
Alternate Identifier(s):
OSTI ID: 1396583
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Engineering Fracture Mechanics
Additional Journal Information:
Journal Volume: 176; Journal Issue: C; Journal ID: ISSN 0013-7944
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Additive manufacturing; Electron beam melting; Ti-6Al-4V; Fatigue crack growth mechanisms; Threshold modeling

Citation Formats

Galarraga, Haize, Warren, Robert J., Lados, Diana A., Dehoff, Ryan R., and Kirka, Michael M.. Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM). United States: N. p., 2017. Web. https://doi.org/10.1016/j.engfracmech.2017.03.024.
Galarraga, Haize, Warren, Robert J., Lados, Diana A., Dehoff, Ryan R., & Kirka, Michael M.. Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM). United States. https://doi.org/10.1016/j.engfracmech.2017.03.024
Galarraga, Haize, Warren, Robert J., Lados, Diana A., Dehoff, Ryan R., and Kirka, Michael M.. Mon . "Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM)". United States. https://doi.org/10.1016/j.engfracmech.2017.03.024. https://www.osti.gov/servlets/purl/1394298.
@article{osti_1394298,
title = {Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM)},
author = {Galarraga, Haize and Warren, Robert J. and Lados, Diana A. and Dehoff, Ryan R. and Kirka, Michael M.},
abstractNote = {Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that fabricates parts by selectively scanning consecutive powder layers with an electron beam. Additive manufacturing technologies are increasing in importance for aerospace and medical applications, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. Ti-6Al-4V is the most widely used and studied alloy for this technology, and is the focus of this work in its Extra Low Interstitial (ELI) variation. The layered manufacturing of metallic components by EBM creates a unique directional microstructure, and consequently, anisotropic properties. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology’s potential extension to high-integrity applications. Here in this study, fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied for different stress ratios and crack growth stages. The interaction between the directional as-fabricated EBM microstructure and FCG was investigated and compared to that of the equiaxed β annealed microstructure obtained by annealing above the β transus temperature. Finally, the FCG threshold, ΔKth, was analytically modeled for the two relative crack propagation directions at different stress ratios, and FCG microstructural mechanisms were established for all three regions of crack propagation.},
doi = {10.1016/j.engfracmech.2017.03.024},
journal = {Engineering Fracture Mechanics},
number = C,
volume = 176,
place = {United States},
year = {2017},
month = {3}
}

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Cited by: 12 works
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    Works referencing / citing this record:

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    • Advanced Engineering Materials, Vol. 20, Issue 5
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    Microstructure simulations of Inconel 718 during selective laser melting using a phase field model
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    A Review of the Fatigue Properties of Additively Manufactured Ti-6Al-4V
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    A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs
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