Page 46 - ESAM-1-2

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

Lastly, a Ni-Al alloy dissimilar material composition process parameters. In the bimetallic structure of Cu/MS1,
was studied by Liu and Dupont. They observed high specimens were fabricated by Tan et al. using LPBF at
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solidification and sub-solidus cracking susceptibility, different scanning speeds (500 – 1,250 mm/s). At low scan
as well as porosity formation. The porosity formation speeds (500 – 950 mm/s), the interface exhibited good
was caused by the use of water-atomized Ni rather than metallurgical bonding. However, at high scan speeds (1,100
gas-atomized Ni, and the cracks were formed due to the and 1,250 mm/s), cracks due to residual stress and pores
combined effect of high thermal stress and brittleness of due to lack of fusion were observed (Figure 8G and H).
the intermetallic. Subsolidus cracking and porosity were High thermal conductive Cu enhanced the metallurgical
formed at the interface due to differences in thermal bonding mechanism through Marangoni convection,
properties. contributing toward interfacial elemental diffusion and
bonding strength.
3.4. Ferrous-, aluminum-, and copper-based
bimetallic alloys 4. Mechanical characteristics of MMAM
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In the Fe/SS (P21/SS316L) bimetallic structure fabricated structures
using MM-LDED, a good metallurgical bonding without Understanding the mechanical properties of an
cracks, pores, or unmelted particles was observed at MM composition is crucial for comprehending its
the interface due to the rapid cooling and steep thermal characteristics. With the potential of manufacturing MM
gradient. The P21 morphology consisted of diminutive samples through AM methods, conducting mechanical
austenite and mostly of martensite. However, the interface testing would expand researchers’ understanding of the
of H13 (ferrous alloy)/Cu was observed to be discrete primary, interfacial, and secondary material properties.
compared to Fe/SS, where micro-cracks and pores were The evaluation of the MMAM structure properties will
observed even though Cu was able to adhere to H13 support the qualification of components fabricated with
(Figure 8A and B). The cracks were formed due to the MMs based on the target regime or environments that the
solidification cracks and higher CTE variation between materials are expected to experience.
H13 and Cu and propagated perpendicularly towards the
H13 region. However, in the 18Ni300/CuSn10 bimetallic This section explores the mechanical properties of
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structure, the interface appeared relatively loose, with small MMAM components, organized according to the types
pores and interfacial mixing of α-Fe and α-Cu phases, as of mechanical tests performed on MM components.
evidenced by scanning electron microscopy and EDS These tests provide crucial insights into the performance
mapping. In contrast, in the CrMn/MS1 (ferrous/ferrous and integrity of the interface between dissimilar
alloy) bimetallic structure, the interface exhibited a good materials. The mechanical evaluations include hardness
metallurgical bonding with no cracks or pores, attributed (Section 4.1), tensile testing (Section 4.2), flexural
to its similar thermal properties. At higher magnification, strength (Section 4.3), compression test (Section 4.4),
a curved solidification characteristic was visible due to the fatigue (Section 4.5), and miscellaneous testing (Section
Marangoni convection (Figure 8C-F). 169 4.6), including wear performance, thermal diffusivity,
and shear bond test. Table 2 provides an overview of
In studies where Al was the base material, Wang et al. all mechanical testing conducted on MMAM to date,
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and Sing et al. investigated Al-12Si/Al-Cu-Mg-Si and categorizing them by microhardness, tensile, flexural,
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Al-12Si/C18400, respectively. In Al-12Si/Al-Cu-Mg-Si, and miscellaneous tests and further categorizing them
the interface exhibited good metallurgical bonding with according to the base material. As shown in Figure 10,
no pores and few defects on the base material due to microhardness and UTS are the most commonly
a similarity in their thermal properties. However, the employed techniques to evaluate the interfacial
Al-12Si/C18400 interface exhibited cracks compared to performance in MM components.
the Al-12Si/Al-Cu-Mg-Si due to the dissimilarities in CTE,
resulting in uneven expansion and contraction during 4.1. Micro-hardness/micro-indentation
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solidification. However, a good metallurgical bonding Hardness testing is often conducted on MMAM specimens
was indicated with a transition region of 200 μm in both as a preliminary test, following the ASTM standard
cases. E384 for small- or large-scale specimens. Hardness
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Both bimetallic structures Cu-Cr/07Cr15Ni5 and T2 testing provides data about the material’s resistance to
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(Cu alloy)/MS1 exhibited defects such as cracks and pores deformation, indentation, scratching, or penetration.
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due to the high thermal conductivity of Cu-Cr, insufficient From the empirical studies collected (Table 2), hardness
energy applied during manufacturing, and variations in testing is one of the most widely adopted testing methods

Volume 1 Issue 2 (2025) 14 doi: 10.36922/ESAM025180010