With ER2319 and B₄C powder as feedstocks and additives, respectively, a wire arc additive manufacturing (WAAM) system based on double-pulse melting electrode inert gas shielded welding (DP-MIG) was used to fabricate single-pass multilayer 2319 aluminum alloy. The results showed that, compared with additive manufacturing component without B₄C, the addition of which can effectively reduce the grain size (from 43 μm to 25 μm) of the tissue in the deposited layer area and improve its mechanical properties (from 231 MPa to 286 MPa). Meanwhile, the mechanical properties are better in the transverse than in the longitudinal direction. Moreover, the strengthening mechanism of B₄C on the mechanical properties of aluminum alloy additive manufacturing mainly includes dispersion strengthening from fine and uniform B₄C granular reinforcing phases and fine grain strengthening from the grain refinement of B₄C. These findings shed light on the B₄C induced grain refinement mechanism and improvement of WAAM 2319 Al alloy.

Wire arc additive manufacturing (WAAM) has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost. However, in the process of automatically manufacturing the high-quality metal parts by WAAM, several problems about the heat build-up, the deposit-path optimization, and the stability of the process parameters need to be well addressed. To overcome these issues, a new WAAM method based on the double electrode micro plasma arc welding (DE-MPAW) was designed. The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically. The effects between the parameters, wire feed rate and torch stand-off distance, in the process of WAAM were investigated experimentally. In addition, a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance. Finally, a series of tests were performed to evaluate the control system’s performance. The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system. Further, the deposition paths about the metal part’s layer heights in WAAM are simplified. Finally, the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.

Twin-wire and arc additive manufacturing (T-WAAM) has potential advantages in improving deposition efficiency and manufacturing functionally graded materials (FGMs), thus attracting much attention. However, there are few studies on the droplet transfer mode of T-WAAM. This paper analyzes the droplet transfer mode and arc swing in the “TIG + AC” twin-wire cross-arc additive manufacturing by in-situ observation with high-speed photography, revealing what factors influence the T-WAAM on deposition shaping the quality and what are the key mechanisms for process stability. Experiments show that with the main arc current provided by TIG 100 A and the twin-wire AC arc current 10 A, three different droplet transfer modes, namely the “free transfer + free transfer, bridge transfer + free transfer, bridge transfer + bridge transfer,” can be observed with the twin wires under different feeding speeds. The corresponding deposition and arc swing are quite different in quality. Through comparative analysis, it is found that the frequent extinguishment and ignition of the arc between electrode wires is the main factor for the instability in the additive manufacturing process. The “bridge transfer + free transfer” mode can obtain a large arc swing angle and a stable deposition, in which the cross arc has a significant stirring effect on the molten pool, and the deposition shape is well-made.