Since the inception, additive manufacturing (AM) continues to grow and change the paradigm of manufacturing for developing advanced materials. One such case is the functionally graded materials (FGM). FGM, in general, is a class of engineered materials, which is identified by a gradual change in composition and/or microstructure of one material into another over a defined volume, causing a variation in properties based on the position. Laser directed energy deposition (LDED) through powder feeding, as one of the AM classifications, is capable of fabricating functionally graded metallic materials. Over the past decade, the number of studies reporting the feasibility of this process in AM of metallic FGMs (AM-FGM) for high-performance applications has dramatically increased. For this reason, the present paper tries to provide a comprehensive review of the state-of-the-art systems in AM-FGM through the LDED process. The reported studies in the field are categorized according to their material system to highlight the opportunities and the challenges associated with each metallic system. Recent findings in processing, phase formation, and properties of different metallic FGMs are summarized and discussed. Finally, the prospects for AM-FGM are presented in an attempt to shed some light on the future research direction.

自成立以来，增材制造（AM）不断增长，并改变了开发先进材料的制造范式。一种这样的情况是功能分级材料（FGM）。一般而言，FGM是一类工程材料，通过一种材料的组成和/或微结构在定义的体积内逐渐转变为另一种材料来识别，从而导致基于位置的特性变化。作为AM分类之一，通过粉末进料进行的激光定向能量沉积（LDED）能够制造功能渐变的金属材料。在过去的十年中，报告了此方法在金属FGM的增材制造（AM-FGM）中用于高性能应用的可行性的研究数量急剧增加。为此原因，本文试图通过LDED过程对AM-FGM中的最新系统进行全面回顾。该领域中已报告的研究根据其材料系统进行了分类，以突出每种金属系统带来的机遇和挑战。总结和讨论了在不同金属FGM的加工，相形成和性能方面的最新发现。最后，介绍了AM-FGM的前景，以期为将来的研究方向提供一些启示。总结和讨论了不同金属FGM的特性和性质。最后，介绍了AM-FGM的前景，以期为将来的研究方向提供一些启示。总结和讨论了不同金属FGM的特性和性质。最后，介绍了AM-FGM的前景，以期为将来的研究方向提供一些启示。