Abstract: In aeronautics and astronautics manufacturing, the design and manufacture of stiffener structures on the cylinder internal wall is widely applied in the improvement of mechanical properties and lightweight design. The hybrid manufacturing method applied inner-wall laser additive manufacturing can effectively form complex internal rib structures and expand their dimensions in the height direction. This study applied the laser additive deposition of AlMgScZr alloy, which enhances the radial rib height of a spun-formed 2219 aluminum alloy cylinder. The thermodynamic behavior simulation analysis and experimental validation of the melt pool are developed. The study investigates the influence of process parameters on the melt pool temperature field, velocity field, and three-dimensional dimensions. The mechanisms of laser energy input, incident powder flow, and thermodynamic boundary conditions on melt movement and melt pool surface morphology evolution is revealed. When the laser power increased from 1000W to 1 600 W, the three-dimensional shape of the melt pool increased quantitatively (length from 1.298 mm to 3.856 mm, width from 1.580 mm to 3.556 mm, and depth from 0.091 mm to 0.725 mm), with the melt pool length increasing by 27.18% (3.856 mm). As the heat transfer mode changes and mass input decreases, the deposition growth rate gradually decreases (from 60.92% to 27.14%). The behavior of the melt is influenced by the combined effects of Marangoni forces and the impact force of the powder. In the length direction, mass input acts on the frontier of the melt pool, causing the melt to move backward; in the width direction, it causes melt reflux. In the deposition direction, the surface melt rate of the lower half of the melt pool is 0.021 m/s and is negative, resulting in a concave surface. The surface velocity vector of the upper half is positive (0.005 7 m/s), leading to a convex surface, with deposited material concentrated on the upper side. As the substrate surface inclination increases, the laser energy density decreases. At an inclination of 30°, the thermal and dynamic conditions of the melt are in a relatively stable equilibrium state; when increased to 45°, the energy density becomes too low, reducing melt flowability, deposition efficiency, and formability.

Key words: laser directed energy deposition, inclined substrate, simulation, melt pool morphology, melt movement behavior