Integrated melt pool and microstructure control for Ti–6Al–4V thin wall additive manufacturing

Abstract In additive manufacturing (AM), melt pool dimension control is needed to accurately build a geometry and determine process precision. Microstructure control is needed for its effect on mechanical properties. This research addresses both for Ti–6Al–4V thin walled structures fabricated by wire feed electron beam AM. Model results show that beam power and beam velocity combinations yielding constant melt pool cross-sectional areas also yield constant solidification cooling rates. Experimental measurements back up this finding and show roughly 20 beta grains across the width of a thin wall deposit which is consistent with an earlier study of single bead deposits, suggesting that links between melt pool geometry and beta grain size are independent of deposition geometry, with significant implications for AM process control.

[1]  S. L. Semiatin,et al.  The effect of laser power and traverse speed on microstructure, porosity, and build height in laser-deposited Ti-6Al-4V , 2000 .

[2]  Karen M. Taminger,et al.  Integrated control of solidification microstructure and melt pool dimensions in electron beam wire feed additive manufacturing of Ti-6Al-4V , 2014 .

[3]  H. Fraser,et al.  Thermal process maps for predicting solidification microstructure in laser fabrication of thin-wall structures , 2006 .

[4]  Jack Beuth,et al.  Process Mapping for Qualification Across Multiple Direct Metal Additive Manufacturing Processes , 2013 .

[5]  Jack Beuth,et al.  Process Maps for Predicting Residual Stress and Melt Pool Size in the Laser-Based Fabrication of Thin-Walled Structures , 2007 .

[6]  J. Hunt,et al.  Steady state columnar and equiaxed growth of dendrites and eutectic , 1984 .

[7]  S. L. Semiatin,et al.  Microstructure and texture evolution during solidification processing of Ti–6Al–4V , 2003 .

[8]  J. Beuth,et al.  The role of process variables in laser-based direct metal solid freeform fabrication , 2001 .

[9]  N. Klingbeil,et al.  Thermal Process Maps for Controlling Microstructure in Laser-Based Solid Freeform Fabrication , 2003 .

[10]  Jack Beuth,et al.  Process Maps for Laser Deposition of Thin-Walled Structures , 1999 .

[11]  J. Beuth,et al.  Process Mapping of Transient Melt Pool Response in Wire Feed E-Beam Additive Manufacturing of Ti-6Al-4V , 2013 .

[12]  Two-Phase Grain Structures.  Standard Test Methods for Determining Average Grain Size Using Semiautomatic and Automatic Image Analysis 1 , 2004 .

[13]  D. Rosenthal,et al.  The Theory of Moving Sources of Heat and Its Application to Metal Treatments , 1946, Journal of Fluids Engineering.

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

[15]  David L. Bourell,et al.  Solid Freeform Fabrication Proceedings , 2001 .

[16]  Jack L. Beuth,et al.  CONTROLLING MELT POOL DIMENSIONS OVER A WIDE RANGE OF MATERIAL DEPOSITION RATES IN ELECTRON BEAM ADDITIVE MANUFACTURING , 2010 .

[17]  Jack Beuth,et al.  A process map for consistent build conditions in the solid freeform fabrication of thin-walled structures , 2001 .

[18]  M. Donachie.  Titanium: A Technical Guide , 1988 .