A review on experimentally observed mechanical and microstructural characteristics of interfaces in multi-material laser powder bed fusion

Abstract

Additive manufacturing (AM) is a revolutionary technology. One of the key AM categories, metal powder-based fusion processes, has many advantages compared to conventional methods for fabricating structural materials, such as permitting increased geometric complexity. While single material metal powder AM has advanced significantly in the past decade, multi-material AM is gradually attracting more attention owing to the recent breakthrough in multi-material feedstock delivery and the growing interest of fabricating functionally graded components. Multi-material AM offers an alternative route for applications that require location dependent material properties and high geometrical complexity. The AM community has invented several ways to achieve compositional gradients and discrete boundaries in two and three dimensions using mechanical spreading, nozzle-based, electrophotographic, and hybrid techniques. This article reviews the current state of laser powder bed fusion based multi-material AM of metals with focuses on the characteristics of the material interface as well as the properties and performance of the AM built functionally graded materials. We show the common challenges and issues related to material transitions, such as defects, segregation, phase separation, and the efficacy of some potential solutions including material and process optimizations. Additionally, this study evaluates the applicability and limitations of the existing testing standards and methods for measuring mechanical performance of functionally graded materials. Finally, we discuss mechanical testing development opportunities, which can help multi-material AM move towards higher technological maturity. In general, we find that the link between gradient microstructure and mechanical properties is not well understood or studied and suggest several mechanical tests that may better inform this knowledge gap.

Joining of Aluminum and CFRP via Laser Powder Bed Fusion: Influence of Experimental Set-Up and Laser Processing on Microstructure and Mechanical Properties

“…As LPBF involves the application and bonding of the initial powder layer on build plates, joining via direct deposition on conventionally manufactured substrates has already been studied for dissimilar metal [ 14 , 15 ] and metal–ceramic [ 16 , 17 ] composites. In the literature, the following challenges were identified for multimaterial LPBF: different thermal properties of the used materials, the formation of brittle intermetallic phases at the interface and the wettability of the melt on the substrate surface [ 16 , 18 ]. These limitations could be overcome by the introduction of specific interlayer materials for a variety of material combinations [ 14 , 15 , 16 , 17 ].…”