Additive Manufacturing of Metal Functionally Graded Materials: A Review

Functionally graded materials (FGMs) have attracted a lot of research interest due to their gradual variation in material properties that result from the non-homogeneous composition or structure. Metal FGMs have been widely researched in recent years, and additive manufacturing has become one of the most important approaches to fabricate metal FGMs. The aim of this paper is to review the research progress in metal FGMs by additive manufacturing. It will first introduce the unique properties and the advantages of FGMs. Then, typical recent findings in research and development of two major types of metal additive manufacturing methods, namely laser metal deposition (LMD) and selective laser melting (SLM), for manufacturing different types of metal FGMs will be discussed. Finally, the major technical concerns in additive manufacturing of metal FGMs which are closely related to mechanical properties, and industrial applications of metal FGMs will be covered.