Achieving high robust aluminum alloy annular laser directed energy deposition based on thermal field assistance system

High thermal conductivity and large fluctuations in laser absorptivity with temperature make aluminum alloy prone to deformations, collapses, spheroidization, and other defects during directed energy deposition (DED) processes. To achieve stable and high-quality annular laser DED (AL-DED) of aluminum alloy, an in situ thermal field assistance system was designed, wherein a preheating-cooling temperature control thermal balance model was established. The thermal field assistance system effect during the AL-DED process of AlSi10Mg has been evaluated, and the control ability of the thermal balance model on absorptivity and temperature field has been analyzed. A continuous 500-layer AL-DED forming of the aluminum alloy was conducted. The results indicate that the in situ thermal field assistance control system can achieve thermal balance during the aluminum alloy component AL-DED process, causing stable laser absorption rate and uniform temperature fields, while reducing surface roughness of components to 2.3 μm. The microstructure and elemental distribution were uniform, transforming the Al–Si eutectic structure from a mesh-like to a dispersed distribution and, consequently, achieving the deposition of a 500-layer, 2.0 mm-thick Al thin-walled component with high dimensional accuracy and stability. This thermal field assistance system effectively improves the stability of absorptivity and the thermal field, providing novel ideas for high-quality AL-DED additive manufacturing of materials sensitive to thermal fields and large absorptivity fluctuations, such as aluminum and copper.