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

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.