Multi-material additive manufacturing of metals: A review of structures and mechanical characteristics

Abstract

The ability to manufacture complex designs from multiple materials has long been a key objective for applications operating in extreme environments. Multi-material (MM) additive manufacturing (MMAM) has significantly enhanced the functionality of additive manufacturing (AM) by enabling the integration of dissimilar alloys while leveraging the inherent advantages of AM, including design flexibility, reduced material waste, and rapid production, with the ability to tailor mechanical properties through spatial material distribution and local processing conditions. This process unlocks unprecedented opportunities across industries such as aerospace, automotive, biomedical, energy, and nuclear sectors. This article provides a comprehensive review of the state-of-the-art in MMAM, focusing on the manufacturing processes, molten pool formation, alloy compatibility, and bimetallic interface characteristics—including microstructural and mechanical properties—as well as modeling and simulation approaches for performance prediction and optimization, with developments tracked from 2013 to 2024. This review article predominantly focuses on: (i) MM-laser powder bed fusion, (ii) MM-directed energy deposition, and (iii) MM-wire-arc AM by detailing the mechanisms of molten pool formation at the interface and dissimilar alloy material compatibilities. Subsequently, the article provides an in-depth analysis of the meso- and micro-structural characteristics at the interface in bimetallic structures across widely employed MMAM alloys. The mechanics of MMs under various mechanical properties are presented, including microhardness/micro-indentation, tensile, flexural, compression, and fatigue strength, which are critical for MMAM applications in extreme conditions. In addition, current modeling and simulation approaches for MMAM are discussed with respect to the challenges and opportunities to increase MMAM adoption. The article concludes with a future roadmap for advancing MMAM by overcoming feedstock and build material cross-contamination, monitoring the in situ process, standardizing MM testing, and further developing thermo-mechanical modeling, specifically, for MMAM.

Graphical abstract

Keywords

Multi-material additive manufacturing / Interfacial boundary layers / Process-structure-property relationships / Three-dimensional printing / Mechanical behavior / Modeling and simulation

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