In-situ micro-impacting assisted directed energy deposition-arc of aluminum alloy: Formability and microstructure

At present, the in-situ forging devices do not have the ability to flexibly adjust impacting forces over a wide frequency range and cannot be easily integrated, which restricts its application on DED-arc (directed energy deposition-arc) technology for additive manufacturing. A novel method and system of in-situ micro-impacting assisted DED-arc based on a compact high-dynamic linear actuator was proposed, developed and verified in arc deposition of 5B06 aluminum alloy. The terminal impacting head could be sufficiently close to the molten pool to enforce the obtaining of flat surface of the deposited layer. The results show that the in-situ micro-impacting could produce accumulating rapid micro-deformation and thus induce a gradient microstructure. DDRX (discontinuous dynamic recrystallization) and CDRX (continuous dynamic recrystallization) hybrid dynamic recrystallization behavior was observed. The microhardness of impacted samples was increased by 9.5 % and 8.0 % in vertical and horizontal direction, respectively. The process of rapid micro-deformation contributes to the retaining of the in-situ work-hardening effect at high temperatures, which made the proposed in-situ impacting method a preferred option for DED-arc additive manufacturing.