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Engineering Science in
Additive Manufacturing Multi-material additive manufacturing of metals

A C

B

Figure 17. Compression behavior of bimetallic lattice structures fabricated through multi-material laser powder bed fusion (MM-LPBF) and multi-
material laser-directed energy deposition (MM-LDED). (A) Finite element modeling-based compression simulation of body-centered cubic and octet
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truss 17-4PH/SS316L lattice structures fabricated through MM-LPBF; (B) Simulation-based compression test on a gyroid bimetallic Ti-6Al-4V/CuA/
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Al-Cu-Mg lattice structure fabricated through MM-LPBF; (C) Compression test on a cylindrical P21/SS316L bimetallic structure fabricated using
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MM-LDED. The finite element analysis results highlight the influence of lattice structure and multi-material additive manufacturing process on
deformation behavior under compressive loading
unique challenges compared to mono-material powder properties to be effective and cannot be generalized to
bed processing. These challenges primarily stem from the most powder combinations. To the best of the authors’
potential for cross-contamination between the materials knowledge, there is currently no comprehensive study
used in fabrication. In monolithic processing, a single on the recycling of leftover powder from MM-LPBF or
powder material is used across the build plate. Additional MM-LDED processes, including the chemical composition
recycling steps are necessary to maintain the particle size/ analysis of separated materials. This recyclability issue
shape distribution and chemical composition of the powder, is specific to MM-LPBF and MM-LDED, as there are
particularly if partial sintering or oxidation has occurred numerous well-established methods for recycling mono-
from repeated use. However, no clear standard currently material powders to control parameters such as powder
exists to define recycling procedures or specify the required size distribution, 209-212 chemical composition, 209-211,213,214
purity of chemical composition after post-processing. This flowability, 209-212,214 and morphology. 211-214 Generally,
lack of standardization complicates the transition to MM powder reuse introduces additional process uncertainties
powder recycling, where up to three powder materials may due to powder degradation. Many studies have reported
be spatially mixed within a single build plate. a moderate reduction in ultimate strength after powder
A few efforts have been made to separate powder reuse, 211,215,216 while others have found no significant
materials, but none have shown significant success. change in mechanical properties following recycling. 217,218
Sieving can separate powders based on particle size The material consumption and associated costs due to
distributions, 175,207,208 but it is ineffective for separating the lack of effective powder recycling methods remain
materials with similar particle sizes. Most powders used in major barriers to the industrial adoption of MMAM. In
LPBF typically fall within a D size distribution of 10 – 90 contrast, wire-fed directed energy deposition and WAAM
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μm. As a result, the Gaussian distribution curves of even avoid this issue by using wire-based feedstocks, thus
dissimilar powders overlap at both the upper and lower circumventing powder waste altogether. However, the
tails, making clean separation infeasible. Other proposed geometric resolution and as-built surface finish provided
methods include separation based on relative density by these wire-based processes are generally insufficient
(using a particle inertia approach) or magnetic properties. for many applications unless extensive post-processing is
However, all three methods require specific material applied.

Volume 1 Issue 2 (2025) 30 doi: 10.36922/ESAM025180010