Regional Control and Optimization of Heat Input during CMT by Wire Arc Additive Manufacturing: Modeling and Microstructure Effects

Abstract

Wire arc additive manufacturing (WAAM) of aluminum-magnesium (Al–Mg) ER5356 alloy deposits is accomplished by cold metal transfer (CMT). During the process, the temperature change of the alloy deposits has a great influence on molding quality, and the microstructure and properties of alloy deposits are also affected by the complex thermal history of the additive manufacturing process. Here, we used an inter-layer cooling process and controlled the heat input process to attempt to reduce the influence of thermal history on alloy deposits during the additive process. The results showed that inter-layer cooling can optimize the molding quality of alloy deposits, but with the disadvantages of a long test time and slow deposition rate. A simple and uniform reduction of heat input makes the molding quality worse, but controlling the heat input by regions can optimize the molding quality of the alloy deposits. The thermophysical properties of Al-Mg alloy deposits were measured, and we found that the specific heat capacity and thermal diffusivity of alloy deposits were not obviously affected by the temperature. The microstructure and morphology of the deposited specimens were observed and analyzed by microscope and electron back-scatter diffraction (EBSD). The process of controlled heat input results in a higher deposition rate, less side-wall roughness, minimum average grain size, and less coarse recrystallization. In addition, different thermal histories lead to different texture types in the inter-layer cooling process. Finally, a controlled heat input process yields the highest average microhardness of the deposited specimen, and the fluctuation range is small. We expect that the process of controlling heat input by model height region will be widely used in the WAAM field.

A Review of the Development Status of Wire Arc Additive Manufacturing Technology

“…Its microstructure and dendrite structure are shown in Figure 6. Chen et al [19] use an interlayer cooling process and control the heat input process to attempt to reduce the influence of thermal history on alloy deposits during the additive process.…”

Preliminary Process and Microstructure Examination of Flux-Cored Wire Arc Additive Manufactured 18Ni-12Co-4Mo-Ti Maraging Steel

“…WAAM offers lower maintenance costs and a higher deposition rate (up to 7-10 kg/h) than other AM processes [2,3]. Both new ways of conducting the process [4][5][6][7][8][9][10], strategies [11,12], and the use of new filler materials are investigated. WAAM parameters have a significant influence on the geometry and microstructure, which was studied by Dinovitzer et al [13].…”

“…The use of additional treatments such as active cooling [17], on-line vortex cooling [18], ultrasonic vibration [19] and post heat treatment [5,20] is examined. The influence of interpass temperature/delay [21] or heat input [8,[22][23][24][25] is analyzed, in the context of distortion and deformations [26,27].…”

Improving the Properties of Laser-Welded Al–Zn–Mg–Cu Alloy Joints by Aging and Double-Sided Ultrasonic Impact Compound Treatment

“…As an aging heat treatment reinforced aluminum alloy, (Al–Zn–Mg–Cu) 7075 aluminum alloy exhibits high specific strength, good fracture toughness, and excellent low cycle fatigue resistance among other characteristics; it is widely used in the fields of transportation, aerospace, and aviation [ 1 , 2 , 3 , 4 ]. Tungsten inert gas welding, metal inert gas welding [ 5 ], plasma arc welding and laser welding are usually used for this alloy. Laser welding exhibits the advantages of a high energy density, fast welding speed, fine grain, high mechanical joint properties, and litter deformation, and achieving a narrow weld with this method is easy [ 6 , 7 , 8 , 9 , 10 ].…”