Arcam AB fka AMAVF

[Tom Joad]

Cast TiAl and EBAMed TiAl have the same density, virtually. Melted TiAl isn't very fluid so to obtain the closest shape to mold requires centrifuge methods. TiAl is very reactive so imperfections increase as exposure to air increases. EBAM TiAl tends to have spherical imperfections from argon (???). EBAM done in a vacuum means the argon must come from powder making process or is a mistake in the link I found. From 2009-

"Argon bubbles carried into the build from the atomized precursor Ti-6Al-4V powders do not appear to vary with increasing melt scans nor do they noticeably influence the tensile behavior of solid monoliths as observed by fracture surface features dominated by varying sizes of ductile dimples."

There's some great metal microstructure "porn" in the following link which also contains the quoted statement above.

Effect of Build Parameters and Build Geometries on Residual Microsturctures and Mechanical Properties of Ti-6Al-4V Components built by Electron Beam Melting

These voids are very small and will make virtually no difference in density. For validation of that I appeal to everyone's sense of proportion. These voids are spherical and therefore, by their geometry, distribute stress better than non-spherical voids. HIP processing removes these voids. I learned that from the Honeywell webcast, so if they do another one, listen in.

There's a description of the problems involved in casting Ti alloys in the patented process below-

Centrifugal Casting of Titanium Alloys, patent