Page 59 - ESAM-1-2

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

powder and its convection flow contributed to the melting phases present in high-strength steel/Ti-6Al-4V bimetallic
of Cu10Sn. Scanning electron microscopy analysis further structures. Using CALPHAD, Wei et al. identified
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revealed that phase migration was likely driven by this three intermetallic formations at the interface: α-Fe +
convection flow, which facilitated elemental intermixing Fe Ti, Fe Ti, and TiFe + β-Ti. Their analysis indicated
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across multiple layers. that a compositional gradient build strategy would not
be sufficient to prevent the formation of Fe Ti, a brittle
Interestingly, Zhang et al. used the Cline–Anthony 196 2
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model to calculate the melt pool temperature field during IMC. In a similar approach, Kannan et al. conducted a
CALPHAD analysis on a compositionally graded Al-Cu-
the LDED process for CuCr/07Cr15Ni5. Using this model,
they successfully predicted printability maps as a function Ce-Zr/SS316L joint. They found that composition ratios
of 90%, 80%, 20%, and 10% SS316L were promising
of deposition layer number. A narrowing of the printability for fabrication, as no primary intermetallic formations
window with increasing layer number was found to were observed. Instead, a BCC 2 matrix formed on the
enhance thermal conductivity, specific heat capacity, and Fe-rich side and an FCC 1 matrix on the Al-rich side.
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effective density. The calculated results from the proposed Scheil simulations performed on a P21/704H bimetallic
analytical model were in good agreement with experimental structure fabricated using MM-WAAM revealed drastic
data. Similarly, Li et al. applied a CFD-based approach to variations in volumetric CTE and freezing range due to the
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model the fabrication process of FGM using MM-LDED. formation of an MC carbide phase from the liquid during
They developed a multiphysics, MM model to simulate solidification. This phase formation led to cracking in the
thermal gradients, phase transitions, melt pool dynamics, intermediate region. Iams et al. performed similar
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and final part geometry, identifying non-uniformities in testing on GRCop-42/IN718 using Scheil simulation
material gradation across the transition zone. Ghanavati and observed the formation of a C15 Cr Nb phase in the
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et al. identified that SS 316L is susceptible to composition GrCop-42 composition. They also reported enrichment
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changes and a lack of fusion, which can lead to porosity in Ni and Fe, which contributed to the formation of the
due to its high equilibrium vapor pressure. In contrast, C14 (Cr,Ni,Fe) Nb phase and the BCC α-Cr phase. In the
IN718 is more prone to distortion, owing to the formation case of Ti-6Al-4V/Al-Cu-Mg structures, which exhibit
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of larger melt pools. In a study involving MM-LPBF TiB / significantly different thermal properties, the interface
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Ti-6Al-4V, Chen et al. used a multilayer finite element was found to be prone to cracking due to the formation
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model (ANSYS) to predict temperature gradients and of IMCs. Based on this understanding, Zhang et al.
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remelting ratios. They assumed that the absorptivity used Scheil–Gulliver simulation and Malac–Distmas
of Ti-6Al-4V is equivalent to that of Ti-alloy powder, calculations to predict the phase diagram and diffusion
while TiB behaves similarly to non-oxide ceramics with path of the bimetallic structure. The binary phase diagram
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relatively high absorptivity. The results showed that the and diffusion path of direct Ti–Al bonding revealed high
maximum temperature gradient occurred at the interface susceptibility to cracking and delamination at the interface
and demonstrated a direct proportionality between laser (top two panels of Figure 16D). To mitigate interfacial
power and temperature gradient (Figure 16A), and an cracking, a Cu interlayer was introduced. The two lower
inverse proportionality with laser scan speed (Figure 16B). panels in Figure 16D show the predicted IMCs. Since
In addition to temperature gradient analysis, a CFD–DEM- Cu is a eutectoid-forming element with both Ti and Al, it
based approach was applied to SS316L/W and W/SS316L contributes to constitutional supercooling and stabilizes
interfaces to examine melt pool temperature profiles the bonding interface.
(Figure 16C). The temperature profiles were evaluated with 132
respect to the melting temperatures of SS316L (1658 K) Beyond thermal behavior, Chen et al. applied a CFD-
and W (3695 K). The observed characteristic behavior is based approach to investigate melt pool morphology
attributed to the significantly higher thermal conductivity in MM-LDED-processed IN625/SS316L (Type-A) and
SS316L/IN625 (Type-B) structures (Figure 15D). In
of W, which facilitates efficient heat dissipation. These Type-A, an anticlockwise flow at the rear of the melt
simulations collectively demonstrate the capabilities of pool contributed to a fully mixed zone by moving
MM thermal-fluid dynamics models in fundamentally remelted SS316L toward regions of higher temperature.
investigating the AM process and assessing printability. In contrast, the Type-B interface exhibited a clockwise
Understanding phase stability and phase flow, causing unmixed IN625 to rise into the melt pool
transformations under variable temperatures, pressures, and become trapped during solidification (Figure 4C and
and compositions is crucial for the development of F for experimental validation). The simulation was used
advanced computational capabilities. In one example, to verify and explain the experimental observations
thermodynamic calculations were employed to predict the previously discussed. Using a similar CFD–DEM-based

Volume 1 Issue 2 (2025) 27 doi: 10.36922/ESAM025180010