Anisotropic tensile behavior of Ti-6Al-4V components fabricated with directed energy deposition additive manufacturing

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Abstract

The present work investigates the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process. The mechanical properties of the component in longitudinal and transverse orientations with respect to the build layers were measured under uniaxial tension. While the average ultimate tensile strength of ∼1060 MPa in both directions agrees well with prior studies on AM Ti-6Al-4V, the achieved elongations of 11% and 14% along the longitudinal and transverse directions, respectively, are higher. The enhanced ductility is partially attributed to the lack of pores present in these components. The anisotropy in ductility is attributed to the columnar prior-β grain morphology and the presence of grain boundary α, which serves as a path along which damage can preferentially accumulate, leading to fracture. In addition, the effect of oxygen on the strength and ductility of the component was studied. The findings indicate that a combined effect of an increase of 0.0124 wt.% oxygen and a decrease in α-lath width due to differential cooling at different heights within the component resulted in an increase of ultimate and yield strengths without a significant loss of ductility. Furthermore, this study demonstrates that quasi-static uniaxial tensile mechanical properties similar to those of wrought Ti-6Al-4V can be produced in an AM component without the need for post-processing heat treatments.

Original languageEnglish (US)
Pages (from-to)309-320
Number of pages12
JournalActa Materialia
Volume87
DOIs
StatePublished - Apr 1 2015

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3D printers
Ductility
Mechanical properties
Oxygen
Yield stress
Elongation
Grain boundaries
Anisotropy
Tensile strength
Heat treatment
Cooling
Processing

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

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title = "Anisotropic tensile behavior of Ti-6Al-4V components fabricated with directed energy deposition additive manufacturing",
abstract = "The present work investigates the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process. The mechanical properties of the component in longitudinal and transverse orientations with respect to the build layers were measured under uniaxial tension. While the average ultimate tensile strength of ∼1060 MPa in both directions agrees well with prior studies on AM Ti-6Al-4V, the achieved elongations of 11{\%} and 14{\%} along the longitudinal and transverse directions, respectively, are higher. The enhanced ductility is partially attributed to the lack of pores present in these components. The anisotropy in ductility is attributed to the columnar prior-β grain morphology and the presence of grain boundary α, which serves as a path along which damage can preferentially accumulate, leading to fracture. In addition, the effect of oxygen on the strength and ductility of the component was studied. The findings indicate that a combined effect of an increase of 0.0124 wt.{\%} oxygen and a decrease in α-lath width due to differential cooling at different heights within the component resulted in an increase of ultimate and yield strengths without a significant loss of ductility. Furthermore, this study demonstrates that quasi-static uniaxial tensile mechanical properties similar to those of wrought Ti-6Al-4V can be produced in an AM component without the need for post-processing heat treatments.",
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AB - The present work investigates the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process. The mechanical properties of the component in longitudinal and transverse orientations with respect to the build layers were measured under uniaxial tension. While the average ultimate tensile strength of ∼1060 MPa in both directions agrees well with prior studies on AM Ti-6Al-4V, the achieved elongations of 11% and 14% along the longitudinal and transverse directions, respectively, are higher. The enhanced ductility is partially attributed to the lack of pores present in these components. The anisotropy in ductility is attributed to the columnar prior-β grain morphology and the presence of grain boundary α, which serves as a path along which damage can preferentially accumulate, leading to fracture. In addition, the effect of oxygen on the strength and ductility of the component was studied. The findings indicate that a combined effect of an increase of 0.0124 wt.% oxygen and a decrease in α-lath width due to differential cooling at different heights within the component resulted in an increase of ultimate and yield strengths without a significant loss of ductility. Furthermore, this study demonstrates that quasi-static uniaxial tensile mechanical properties similar to those of wrought Ti-6Al-4V can be produced in an AM component without the need for post-processing heat treatments.

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