  Rapid cooling rates and stochastic interactions between the heat source and
feedstock in additive manufacturing (AM) result in strong anisotropy and
process-induced defects deteriorating the tensile ductility and fatigue
resistance of printed parts. We show that by deliberately introducing a high
density of lack of fusion (LoF) defects, a processing regime that has been
avoided so far, followed by pressure assisted heat treatment, we can print
Ti-6Al-4V with reduced texture and exceptional properties surpassing that of
wrought, cast, forged, annealed, and solution-treated and aged counterparts.
Such improvement is achieved through the formation of low aspect ratio
{\alpha}-grains around LoF defects upon healing, surrounded by {\alpha}-laths.
This occurrence is attributed to surface energy reduction and recrystallization
events taking place during healing of LoF defects. Our approach to design
duplex microstructures is applicable to a wide range of AM processes and alloys
and can be used in the design of damage tolerant microstructures.

Materials Science;Applied Physics