Intra-layer closed-loop control of build plan during directed energy additive manufacturing of Ti–6Al–4V

• Developed intra-layer, closed-loop control of additive manufacturing build plan.
• Control affected macrostructure, microstructure, and mechanical properties.
• Demonstrated reduced variability in microstructure and hardness with control.

The location, timing, and arrangement of depositions paths used to build an additively manufactured component – collectively called the build plan – are known to impact local thermal history, microstructure, thermal distortion, and mechanical properties. In this work, a novel system architecture for intra-layer, closed-loop control of the build plan is introduced and demonstrated for directed-energy deposition of Ti–6Al–4V. The control strategy altered the build plan in real time to ensure that the temperature around the start point of each hatch, prior to deposition, was below a threshold temperature of 415 °C. Potential hatches with an initial temperature above this threshold were temporarily skipped. Compared with open-loop processing, closed-loop control resulted in vertical alignment of columnar prior-β grains, more uniform α-lath widths, and more-uniform microhardness values within the deposited component.