Thermal boundary evolution of molten pool during wire and arc additive manufacturing of single walls of 5A06 aluminum alloy

Molten pool uniformity is a prerequisite for wire and arc additive manufacture to achieve a uniform surface appearance. The thermal boundary is a key indicator to evaluate the thermodynamic state of the molten pool. This paper focuses on thermal analysis through finite element simulation and characterizes the thermal evolution of a molten pool during bottom-up deposition. The peak temperature of the substrate plate increases from 375.7 °C to 623.1 °C when peak current increases from 120 A to 180 A. The temperature gradient decreases from 40 °C/mm to 30 °C/mm. Weld speed increases from 0.15 m/min to 0.25 m/min; the temperature gradient is kept at about 30 °C/mm. Dimensionless thermal conductivity, Ge number, is proposed and defined as the criteria to estimate layer size variation. For I_p = 140 A, the average value of the Ge number is 87.7, and it shows the best numerical stability. Dimensionless thermal conductivity, Ge, is proposed and defined as the criteria to estimate the occurrence of layer size variation. Prolonging heating time and increasing cycle frequency, Ge number shows favorable stability during bottom-up deposition. The experimental results are consistent with analytical conclusions, which proves the validity of the Ge number as an indicator of deposition stability.