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A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 1 8 2 0 • Promotion of a beta eutectoid trans- formation ( β → α + TiH 2 ) • Expansion of the bcc beta phase unit cell by 5.4% • Increase in specific volume (hydride has a 17% greater specific volume than the matrix) These effects refine and recrystal- lize the microstructure. Examples of the effects of THP on microstructure are shown in Fig. 8. Sun et al. [6] further developed the THP technique via hydrogen-assisted production of low-cost spherical melt- less titanium powder (Fig. 9). Oxygen content of the powder is reduced to 0.2 w/o at a 50% lower cost than that of conventional hydride-dehydride powder. ~AM&P Fig. 9 — Schematic of the granulation-sintering-deoxygenation (GSD) process. Hydrided Ti-6Al-4V or blended elemental material is prepared by ball milling in a solvent to reduce the particle size to <10 µm, adding a thermoplastic binder to facilitate formation of granules, spray drying with argon gas to form spherical granules of Ti-6Al-4V hydride, thermally debinding using an inorganic separator to prevent granules from sintering together, and deoxidizing sintered spherical Ti-6Al-4V powder using calcium or magnesium (with an O 2 content tailored in the range of 0.08-0.20 wt%). For more information: Professor Sam Froes is a consultant to the additive manufacturing and titanium industries. He may be reached at 253.517.3034 or ssfroes@comcast.net. References 1. F.H. Froes, D. Eylon, and H.B. Bom- berger (editors), Titanium Technology: Present Status and Future Trends, Titanium Development Assoc. (now International Titanium Assoc.), 1985. 2. F.H. Froes, Titanium Powder Metal- lurgy: Developments and Opportunities in a Sector Poised for Growth, Powder Met. Reviews, Vol 2, No. 4, p 29-43, 2013. 3. B. Dutta and F.H. Froes, Additive Manufacturing of Titanium Alloys, Else- vier/Butterworth-Heinemann, 2016. 4. C.M. Ward-Close and F.H. Froes, Developments in the Synthesis of Light- weight Metals, J. of Metals, p 27-30, Jan. 1994. 5. F.H. Froes,O.N. Senkov, andJ.I.Qazi, Hydrogen as a Temporary Alloying Ele- ment in Titanium Alloys: Thermohy- drogen Processing, Intl. Matls. Rev., 2004, Vol 49, No. 3-4, p 227-245, 2004. 6. P. Sun, et al., A Novel Method for Production of Spherical Ti-6Al-4V Pow- der for Additive Manufacturing, Powder Technol., 301, p 331-335, 2016.