Microstructure and Mechanical Properties of Wire and Arc Additive Manufactured Ti-6Al-4V

Wire and arc additive manufacturing (WAAM) is a novel manufacturing technique in which large metal components can be fabricated layer by layer. In this study, the macrostructure, microstructure, and mechanical properties of a Ti-6Al-4V alloy after WAAM deposition have been investigated. The macrostructure of the arc-deposited Ti-6Al-4V was characterized by epitaxial growth of large columnar prior-β grains up through the deposited layers, while the microstructure consisted of fine Widmanstätten α in the upper deposited layers and a banded coarsened Widmanstätten lamella α in the lower layers. This structure developed due to the repeated rapid heating and cooling thermal cycling that occurs during the WAAM process. The average yield and ultimate tensile strengths of the as-deposited material were found to be slightly lower than those for a forged Ti-6Al-4V bar (MIL-T 9047); however, the ductility was similar and, importantly, the mean fatigue life was significantly higher. A small number of WAAM specimens exhibited early fatigue failure, which can be attributed to the rare occurrence of gas pores formed during deposition.

[1]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[2]  David M. Keicher,et al.  The laser forming of metallic components using particulate materials , 1997 .

[3]  Z. M. Wang,et al.  Titanium alloys and their machinability—a review , 1997 .

[4]  G. Lütjering.  Influence of processing on microstructure and mechanical properties of (α+β) titanium alloys , 1998 .

[5]  M. Mills,et al.  Room temperature deformation and mechanisms of slip transmission in oriented single-colony crystals of an α/β titanium alloy , 1999 .

[6]  G. K. Lewis,et al.  Practical considerations and capabilities for laser assisted direct metal deposition , 2000 .

[7]  Wilfried Kurz,et al.  Columnar to equiaxed transition in solidification processing , 2001 .

[8]  A. ADoefaa,et al.  ? ? ? ? f ? ? ? ? ? , 2003 .

[9]  W. Kurz,et al.  Epitaxial deposition of MCrAlY coatings on a Ni-base superalloy by laser cladding , 2003 .

[10]  T. Palmer,et al.  In situ observations of phase transitions in Ti–6Al–4V alloy welds using spatially resolved x-ray diffraction , 2003 .

[11]  S. Kelly,et al.  Microstructural evolution in laser-deposited multilayer Ti-6Al-4V builds: Part II. Thermal modeling , 2004 .

[12]  Wei Zhang,et al.  Phase transformation dynamics during welding of Ti–6Al–4V , 2004 .

[13]  S. Kelly,et al.  Microstructural evolution in laser-deposited multilayer Ti-6Al-4V builds: Part I. Microstructural characterization , 2004 .

[14]  A. Jawaid,et al.  The effect of machining on surface integrity of titanium alloy Ti–6% Al–4% V , 2005 .

[15]  J. Mendez,et al.  Slip and fatigue crack formation processes in an α/β titanium alloy in relation to crystallographic texture on different scales , 2008 .

[16]  P. Castany,et al.  In situ transmission electron microscopy deformation of the titanium alloy Ti–6Al–4V: Interface behaviour , 2008 .

[17]  Bernd Baufeld,et al.  Mechanical properties of Ti-6Al-4V specimens produced by shaped metal deposition , 2009, Science and technology of advanced materials.

[18]  A. Short.  Gas tungsten arc welding of α + β titanium alloys: a review , 2009 .

[19]  S. S. Al-Bermani,et al.  The Origin of Microstructural Diversity, Texture, and Mechanical Properties in Electron Beam Melted Ti-6Al-4V , 2010 .

[20]  T. C. Lindley,et al.  The role of microtexture on the faceted fracture morphology in Ti–6Al–4V subjected to high-cycle fatigue , 2010 .

[21]  Stewart Williams,et al.  Morphology investigation on direct current pulsed gas tungsten arc welded additive layer manufactured Ti6Al4V alloy , 2011 .

[22]  Omer Van der Biest,et al.  Wire based additive layer manufacturing: Comparison of microstructure and mechanical properties of Ti–6Al–4V components fabricated by laser-beam deposition and shaped metal deposition , 2011 .

[23]  W. Marsden.  I and J , 2012 .

[24]  Paul A. Colegrove,et al.  Investigation of the benefits of plasma deposition for the additive layer manufacture of Ti–6Al–4V , 2012 .