Optimising the mechanical properties of Ti-6Al-4V components produced by wire + arc additive manufacturing with post-process heat treatments

Wire + Arc Additive Manufacturing (WAAM) is a promising manufacturing process for producing large aerospace components. Based on welding technology, the process is highly affordable, has a very high deposition rate and is not limited by chamber size. Ti-6Al-4V is a promising candidate material for this technology given that it is extensively used in aerospace applications and some large, high buy-fly ratio components can be more efficiently produced by WAAM than via the conventional machining from billet approach. There is currently limited knowledge about whether additional post processes including heat treatments and hot isostatic pressing are necessary to unlock the optimal mechanical properties of Ti-6Al-4V components produced by WAAM. This work explores a range of different post process treatments and the effects on the microstructure and tensile properties of Ti-6Al-4V components produced by WAAM. The relatively slow cooling rate (10-20Ks(-1)) during the beta-alpha transformation produced Widmanstatten-alpha and offered an optimal balance between strength and ductility. Hot Isostatic Pressing (HIPing) removed gas porosity but was not effective in improving strength or ductility. Residual tensile stresses in as-built components severely impair ductility and should be removed through stress relief treatments. (C) 2018 Elsevier B.V. All rights reserved.

[1]  S. Semiatin,et al.  Coarsening behavior of an alpha-beta titanium alloy , 2004 .

[2]  H. J. Rack,et al.  Phase transformations during cooling in α+β titanium alloys , 1998 .

[3]  Changmeng Liu,et al.  Obtaining fine microstructure and unsupported overhangs by low heat input pulse arc additive manufacturing , 2017 .

[4]  M. Bermingham,et al.  Sensitivity of Ti-6Al-4V components to oxidation during out of chamber Wire + Arc Additive Manufacturing , 2018, Journal of Materials Processing Technology.

[5]  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 .

[6]  Galina Kasperovich,et al.  Improvement of fatigue resistance and ductility of TiAl6V4 processed by selective laser melting , 2015 .

[7]  M. Bermingham,et al.  Effect of trace lanthanum hexaboride and boron additions on microstructure, tensile properties and anisotropy of Ti-6Al-4V produced by additive manufacturing , 2018 .

[8]  Jaimie Tiley,et al.  Quantification of microstructural features in α/β titanium alloys , 2004 .

[9]  Philip B. Prangnell,et al.  Effect of build geometry on the β-grain structure and texture in additive manufacture of Ti6Al4V by selective electron beam melting , 2013 .

[10]  B. Baufeld,et al.  Additive manufacturing of Ti–6Al–4V components by shaped metal deposition: Microstructure and mechanical properties , 2010 .

[11]  Matthew Roy,et al.  Residual stress of as-deposited and rolled wire+arc additive manufacturing Ti–6Al–4V components , 2016 .

[12]  P. Kobryn,et al.  Mechanical Properties of Laser-Deposited Ti-6Al-4V , 2001 .

[13]  Zengxi Pan,et al.  Wire-feed additive manufacturing of metal components: technologies, developments and future interests , 2015 .

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

[15]  Chong Soo Lee,et al.  An analysis of the strain hardening behavior of ultra-fine grain pure titanium , 2006 .

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

[17]  Christoph Leyens,et al.  Mechanical properties of additive manufactured titanium (Ti–6Al–4V) blocks deposited by a solid-state laser and wire , 2011 .

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

[19]  H. Maier,et al.  On the mechanical behaviour of titanium alloy TiAl6V4 manufactured by selective laser melting: Fatigue resistance and crack growth performance , 2013 .

[20]  Matthew S. Dargusch,et al.  Controlling the microstructure and properties of wire arc additive manufactured Ti–6Al–4V with trace boron additions , 2015 .

[21]  H. Fraser,et al.  Effects of process variables and size-scale on solidification microstructure in beam-based fabrication of bulky 3D structures , 2009 .

[22]  C. Colin,et al.  As-Fabricated and Heat-Treated Microstructures of the Ti-6Al-4V Alloy Processed by Selective Laser Melting , 2011 .

[23]  Philip Nash,et al.  Finite-element analysis and experimental validation of thermal residual stress and distortion in electron beam additive manufactured Ti-6Al-4V build plates , 2016 .

[24]  R. Poprawe,et al.  Laser additive manufacturing of metallic components: materials, processes and mechanisms , 2012 .

[25]  Christoph Leyens,et al.  Additive manufactured Ti-6Al-4V using welding wire: comparison of laser and arc beam deposition and evaluation with respect to aerospace material specifications , 2010 .

[26]  Todd Palmer,et al.  Anisotropic tensile behavior of Ti-6Al-4V components fabricated with directed energy deposition additive manufacturing , 2015 .

[27]  B. Baufeld,et al.  Young’s modulus and damping in dependence on temperature of Ti–6Al–4V components fabricated by shaped metal deposition , 2011 .

[28]  M. Brandt,et al.  In situ tailoring microstructure in additively manufactured Ti-6Al-4V for superior mechanical performance , 2017 .

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

[30]  Sanjooram Paddea,et al.  Fatigue crack propagation behaviour in wire+arc additive manufactured Ti‐6Al‐4V: Effects of microstructure and residual stress , 2016 .

[31]  Xiaolong Wang,et al.  Three-Dimensional Finite Element Analysis with Clamping in Wire and Arc Additive Manufacturing , 2016, 2016 European Modelling Symposium (EMS).

[32]  Eui W. Lee,et al.  Correlation of fatigue properties and microstructure in investment cast Ti-6Al-4V welds , 2003 .

[33]  P. Colegrove,et al.  Microstructure and Mechanical Properties of Wire and Arc Additive Manufactured Ti-6Al-4V , 2013, Metallurgical and Materials Transactions A.

[34]  Young‐kook Lee,et al.  Effect of grain size on tensile properties of fine-grained metastable β titanium alloys fabricated by stress-induced martensite and its reverse transformations , 2012 .

[35]  William E. Frazier,et al.  Metal Additive Manufacturing: A Review , 2014, Journal of Materials Engineering and Performance.

[36]  Heat treatment of Ti6Al4V produced by Selective Laser Melting: Microstructure and mechanical properties , 2012 .

[37]  Konrad Wissenbach,et al.  Ductility of a Ti‐6Al‐4V alloy produced by selective laser melting of prealloyed powders , 2010 .