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

behavior was attributed to surface roughness, dimensional effects, including thermal diffusivity and wear
deviation of the upper surface, and unevenness of the performance, which are critical for specific application
bottom surface. 189 domains. Understanding thermal diffusivity is vital for
characterizing the heat transfer behavior of MMAM
4.5. Fatigue life structures during manufacturing. Thermal diffusivity data
Fatigue testing remains a fundamental approach for provides information on a material’s ability to conduct
assessing the failure mechanisms of structural components heat relative to its ability to store it. Figure 14 presents both
under cyclic loading. Its application in bimetallic structures experimental and theoretical thermal diffusivity data for
has gained increasing attention in recent years. Unlike MMAM structures with IN718 as the base material, along
other mechanical properties such as tensile strength and with data for the constituent single-alloy materials. The
hardness, fatigue failure often occurs without prior visible comparison illustrates how the thermal performance of the
deformation, potentially leading to catastrophic structural bimetallic system differs from its monolithic counterparts.
failures. As a result, fatigue testing is considered a critical Theoretical thermal diffusivity values of the bimetallic
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indicator of dynamic mechanical performance, providing structures range from 14.37 to 17.09 mm /s between
essential insights into the service life and reliability of MM 50°C and 300°C.In contrast, experimental values were
structures, especially in high-cycle applications involving found to be lower, ranging from 10.30 ± 07 to 12.33 ± 0.07
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alternating stresses. mm /s within the same temperature range. The thermal
diffusivity of the bimetallic structure lies between those of
In a notable study, Tan et al. investigated the monolithic IN718 and the Cu alloy, reflecting the expected
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fatigue behavior of MMAM structures with ferrous base thermal blending behavior.
materials, specifically C300MS/AISI304 and C300MS/
AISI1045CS. Both bimetallic structures were evaluated at In addition to thermal behavior, wear performance was
30 Hz under 400 MPa stress. C300MS/AISI304 exhibited also investigated. Wear testing was conducted on an IN718/
a significantly longer fatigue life of 4.505 × 10 , compared SS316L MMAM structure with carbon fiber functioning
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to 0.36 × 10 cycles for C300MS/AISI1045CS. Failure in as the IBL. The analysis included comparative wear data
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C300MS/AISI304 occurred on the AISI304 side, whereas for both IN718 and IN718/CF/SS316L. Results showed
in C300MS/AISI1045CS, failure initiated at the interface. that IN718/CF/SS316L reached a steady-state wear rate in
Fractographic analysis revealed that the premature failure under 80 seconds, significantly faster than wrought IN718,
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of C300MS/AISI1045CS was caused by the presence of which stabilized after approximately 300 s.
interfacial pores, while the defect-free interface in C300MS/ 5. Modeling and simulation for MMAM
AISI304 contributed to its superior fatigue resistance.
An extensive list of in-process and post-fabrication
The fatigue life of bimetallic IN718/SS316L was further simulation software and codes currently exists for single-
examined through two configurations: crack arrester and material AM across multiple length scales, providing
crack divider. Results indicated that the crack growth rate insights into the state of research and development toward
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was influenced by the local crack tip stress intensity factor MMAM. Experimental investigations are often time-
range (∆K). Depending on the transition direction (soft- consuming and costly, making them prohibitive for some
to-hard or hard-to-soft), crack propagation was affected AM research. Consequently, simulations play a critical role
by differences in material properties and grain structure. in augmenting understanding, optimizing processes, and
Fractographic analysis revealed that grain orientation enabling process control. Simulations commonly used in
and morphology significantly impacted crack tortuosity single-material AM include thermodynamic modeling,
and propagation rate. Although dissimilar material melt pool dynamics, powder bed behavior (PBB), and
interfaces did not show a pronounced effect under high computational fluid dynamics-volume of fluid (CFD-
∆K conditions, crack behavior was markedly influenced by VOF) models. Thermal simulation modeling is employed
grain structure at lower ∆K values. Overall, Duval-Chaneac to guide parameter selection, ranging from single melt
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et al. concluded that residual stress had minimal effect pool point penetration to single or multiple melt pool
on crack propagation due to careful specimen preparation tracks, and extending to full component modeling at
and the good coherence of grain structures at the interface. micro-, meso-, and macro-length scales. Melt pool
dynamic simulations focus on material behavior during
4.6. Miscellaneous tests
interaction with the laser and heat-affected zone, providing
While most studies have focused on common and widely information on melt pool morphology, cooling rates, and
available mechanical properties such as hardness and microstructural characteristics. PBB simulations model
tensile strength, some have explored environmental particle–particle interactions on the powder bed, powder

Volume 1 Issue 2 (2025) 24 doi: 10.36922/ESAM025180010