The effect of direct energy deposition arc mode on the porosity of AA5087 aluminum alloy

Abstract

The paper evaluates the effect of the welding mode of the CMT-based direct energy deposition arc (DED-Arc) process on the porosity of AA5087 aluminum alloy walls. Three welding modes were used to produce the walls: cold metal transfer (CMT), CMT-Pulse (CMT-P), and CMT Cycle-Step (CMT-CS) with heat inputs of 128.5 J/mm, 150.4 J/mm, and 152 J/mm, respectively. Porosity was assessed with a light microscopy (LM) and computer tomography (CT). The wall produced with the lowest heat input had the lowest average porosity of 0.641 % compared to CMT-P (0.799 %) and CMT-CS (0.766 %). CT results followed the same trend with porosity of 0.21 %, 0.32 %, and 0.27 % for CMT, CMT-P, and CMT-CS, respectively. The porosity level strongly correlates with the hydrogen content. The lowest porosity (CMT) at the lowest hydrogen content (5.29 ppm) is associated with lower hydrogen solubility in a molten pool at lower heat inputs. Most of the detected pores in all modes ranged from 51 to 100 μm in size.