Abstract
A novel on-line vortex cooling powered by low-cost compressed air was proposed to reduce common defects such as low forming precision, coarse grains, and pores caused by heat accumulation in the Wire Arc Additive Manufacturing (WAAM) of aluminum alloy. The impacts of interlayer cooling (IC), substrate cooling (SC), on-line cooling (OL), and natural cooling (NC) processes were compared on the morphology, microstructure, and mechanical properties of as-deposited walls, revealing that the OL process significantly lowers the interlayer temperature and improves forming precision. The high cooling rate produced by the OL process reduced the absorption of hydrogen in the molten pool, lowering porosity. Furthermore, the grains are refined due to the developed undercooling. However, the high cooling rate enhanced the segregation potential of Mg element and raised the content of the β phase. Conclusively, the maximum tensile strength, elongation, and microhardness of the as-deposited wall are achieved via the OL process, and the fine-grain strengthening mechanism plays an important role in improving mechanical properties. The OL process is cheaper and poses a significant effect; it is highly suitable for the additive manufacturing of complex components compared with other forced cooling processes.
Highlights
The newly introduced digital additive manufacturing technology works by depositing metal parts in layerwise [1]
Three different cooling processes were conducted in the Wire Arc Additive Manufacturing (WAAM) 5356 alloys
The major findings include: In the WAAM process for the Al–Mg alloy, the adoption of the on-line cooling (OL) process maintained a minimum interlayer temperature, and the as-deposited wall thickness was the easiest to control to a specified size; in particular, the arc pit at the end of the wall was not visible which improved the stability of the
Summary
The newly introduced digital additive manufacturing technology works by depositing metal parts in layerwise [1]. In recent years, compared with Laser Depositing Manufacturing (LDM) [3] and Selective Laser Melting (SLM) [4], Wire Arc Additive Manufacturing (WAAM) has attracted far more attention in the field of additive manufacturing, for example, in the aerospace field [5,6] This is attributed to its lower initial cost, higher forming efficiency, and higher material utilization [5,6]. Ren et al [9] studied interpass cooling (200, 160, 120 and 80 ◦ C) of Al–6.3Mg alloy which adopted the cold metal transfer advanced process during WAAM process. Henckell et al [12] studied the energy input in WAAM with Gas Metal Arc Welding (GMAW), whereby they reduced welding energy input to lead to an adaptation of geometrical and microstructural features of additively manufactured work pieces. We analyzed the influence on the results and assessed the reliability of the control WAAM
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