Metal additive manufacturing technologies, such as powder bed fusion process, directed energy deposition (DED) process, sheet lamination process, etc., are one of promising flexible manufacturing technologies due to direct fabrication characteristics of a metallic freeform with a three-dimensional shape from computer aided design data. DED processes can create an arbitrary shape on even and uneven substrates through line-by-line deposition of a metallic material. Theses DED processes can easily fabricate a heterogeneous material with desired properties and characteristics via successive and simultaneous depositions of different materials. In addition, a hybrid process combining DED with different manufacturing processes can be conveniently developed. Hence, researches on the DED processes have been steadily increased in recent years. This paper reviewed recent research trends of DED processes and their applications. Principles, key technologies and the state-of-the art related to the development of process and system, the optimization of deposition conditions and the application of DED process were discussed. Finally, future research issues and opportunities of the DED process were identified.

金属增材制造技术，例如粉末床熔合工艺，定向能量沉积（DED）工艺，薄板层压工艺等，由于具有三维形状的金属自由形式的直接制造特性而成为很有前途的柔性制造技术之一。计算机辅助设计数据。DED工艺可通过逐行沉积金属材料在平坦和不平坦的基板上创建任意形状。这些DED工艺可以通过连续和同时沉积不同的材料来容易地制造具有所需特性和特性的异质材料。此外，可以方便地开发将DED与不同制造工艺相结合的混合工艺。因此，近年来对DED工艺的研究一直在稳步增长。本文回顾了DED工艺及其应用的最新研究趋势。讨论了与工艺和系统开发，沉积条件的优化以及DED工艺的应用有关的原理，关键技术和最新技术。最后，确定了DED流程的未来研究问题和机会。