Additive manufacturing of functionally graded metallic materials: A review of experimental and numerical studies

Inspired by nature, advanced functionally graded materials (FGMs) are an appropriate response to high-performance multi-functional applications. The introduction of modern additive manufacturing technology to the processing of gradient metallic materials opened up a great opportunity for further development of this class of engineering materials owing to several advantages of this technology, e.g., high manufacturing flexibility. The phenomena prevailing in the additive manufacturing of gradient metallic materials, such as melting and solidification, have drawn special attention to this field from the viewpoint of materials science and engineering to the extent that many experimental and numerical research studies have been done in this regard in recent years. After briefly introducing FGMs and providing a brief overview of manufacturing methods with a focus on additive manufacturing processes, this paper discusses experimental studies in three sections: metal–metal, metal-ceramic, and metal-intermetallic gradient materials. Then, numerical studies are reviewed from the perspective of materials science and engineering. In the end, important results achieved so far are summarized and an outlook is provided for further research in the future.