Progress In recent years, significant breakthroughs have been made in the LDED process for aluminum alloys, titanium alloys, nickel-based superalloys, and their composites. The introduction of rare earth elements, such as Sc and Zr, for microalloying modifications and the addition of nanoparticles address challenges such as hot cracking, excessive defects, and the limitations of a single strengthening mechanism that leads to insufficient performance in aluminum alloys. This advancement enables the preparation of various high-density and high-performance aluminum alloy materials, including Al-Mn-Sc, TiB₂/Al-Mg-Sc-Zr, and 6061-RAM2. Additionally, the development of a range of titanium alloys and their composites suitable for the LDED process, such as Ti-Cu, Ti-O-Fe, and TiB/TC4, eliminates coarse columnar crystal structures in favor of uniform and fine equiaxed crystal structures. This development is expected to address the longstanding challenge of performance anisotropy in additive manufacturing titanium alloys. Issues such as the suppression of solidification and liquation cracks, microstructure refinement, uniformity improvement, and performance enhancement in nickel-based/nickel-iron-based superalloys, including IN 718, IN 625, and HR-1, have been resolved. These solutions lead to a significant performance improvement in the prepared materials, with the IN 718 and IN 625 superalloys achieving performance levels comparable to forged materials of the same grade.This paper first summarizes the current research status of LDED technology applied to three primary structural materials in aerospace equipment.

Currently, the LDED process for metal materials faces challenges such as hard-to-manage defects, uneven microstructures, insufficient strength and toughness, low manufacturing efficiency, and poor surface quality. In response, researchers domestically and internationally have developed various new high-performance, high-efficiency, and high-precision LDED processes aimed at enhancing performance, deposition efficiency, and manufacturing accuracy. By employing external fields such as acoustic, deformation, and magnetic fields to assist LDED, significant strides have been made in eliminating defects, refining microstructures, and improving performance. The development of laser processing heads with high deposition rates, multi-channel deposition equipment, and processes have boosted deposition efficiency. Additionally, the creation of high-precision powder feeding nozzles and additive-subtractive hybrid manufacturing equipment and processes has enhanced the quality of deposited surfaces. Notably, the Fraunhofer Institute for Laser Technologys development of three-dimensional EHLA technology has achieved manufacturing accuracy of up to 100 µm and a deposition efficiency of up to 532 cm³/h, setting a benchmark for the future direction of LDED technology.

As LDED processes for aluminum alloys, titanium alloys, nickel-based superalloys, and their composites mature and stabilize, alongside the development of new, high-performance, high-efficiency, and high-precision processes, LDED technology has realized significant applications in aerospace. This includes use in critical areas, such as launch vehicles and manned spacecrafts main load-bearing components, as well as in the manufacturing of copper alloy/superalloy heterogeneous alloy combustion chambers and integrated nozzles for rocket engines. The aerospace industrys demand for lightweight, integrated, high-temperature-resistant, and high-precision equipment has propelled the development and industrial application of LDED technology.

Large-scale, integrated, lightweight, and high-precision structures are becoming crucial trends in the development of aerospace equipment. Laser directed energy deposition (LDED) technology, with its high forming efficiency, flexible material feeding methods, and extensive freedom in shaping, proves to be highly suitable for the evolving trends in aerospace equipment development. It has gained significant traction in sectors such as launch vehicles, manned spacecraft, and rocket engines, positioning the aerospace industry as a key driver in the development and application of LDED technology. However, the current progress in LDED additive manufacturing technology is not adequately aligned with industry needs. This misalignment leads to underutilization of its technical advantages, vague directions for technological development, and limited application scenarios and fields. To expedite the technologys industrialization and intelligent evolution, and to achieve large-scale, systematic applications, it is essential to review and document the current research and application advancements of LDED for large-scale metal components in aerospace. This involves examining material research, process development, and application progress, and identifying future directions for LDED technology.

aluminum alloy, titanium alloy, nickel-based superalloy, and their composites. Building on this foundation, it organizes the development directions and research progress of LDED processes. It then delves into the manufacturing challenges, research, and application advancements of three typical aerospace equipment structures: the main load-bearing structure, the integrated structure of heterogeneous alloy, and the integrated structure with integrated flow channels. Lastly, the paper forecasts the development trajectory of materials, processes, and equipment for LDED additive manufacturing technology, highlighting the following strategic directions: the promotion of dedicated high-performance alloy materials design and development, tailored to the unique non-equilibrium physical metallurgy characteristics of the LDED process; the acceleration of high-precision LDED process, equipment, and software research and development, including the high-precision formation of large complex structures; the advancement of additive and subtractive hybrid manufacturing technology research; and the hastening of low-cost LDED manufacturing technology development.