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

Table 1. A comprehensive summary of the empirical literature on the metallurgical bonding in bimetallic multi‑material additive
manufacturing
Deposited material Titanium Stainless Nickel alloy Aluminum Copper alloy Ferrous Miscellaneous
Base material alloy steel alloy alloy alloy alloy
Stainless steel alloy 122,123 124,125 91,126-138 50 33,56,58,128, 147 148,149
139-146
Titanium alloy 150-153 154 155 — 55 — —
Nickel alloy 52,156 91,131,132, — — 47,162,163 164 —
157-161
Ferrous alloy 165 166 — — 167,168 169,170 171
Aluminum alloy — — — 172-174 175 176 177
Copper alloy — 178 — — 179 — —

features and mechanical properties. In FGM, the element an interlayer can be used to resolve the problem. Apart
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composition typically varies throughout the structure, from the intermetallic formation, the thermal property
with the ratio of elements varying with respect to the disparity between dissimilar alloys plays a significant role
build height. A minor deviation in element content from in metallurgical bonding.
the intended composition could disrupt the alloy’s The disparity between the thermal properties of
performance and fundamental properties. In the discrete dissimilar alloys, such as melting temperature, CTE, and
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MMAM, the abrupt change of composition could act as a thermal conductivity, is one of the issues that contribute
chemical potential gradient that drives alloying elements to weaker metallurgical bonding. During the MMAM
and impurities from one side to another, leading to failure process, significant differences in melting temperature not
mechanisms. Similar behavior could be observed in a only lead to a non-uniform heat flow and dilution but also
steep property gradient of FGM, which serves as a residual tend to cause cracking on the low melting temperature alloy
stress concentration site during manufacturing. Besides side during solidification (e.g., SS316L/W). The cracking
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the chemical composition of the alloys, properties such as attributed to this mismatch in melting temperature can
thermal conductivity and melting temperature can prevent be mitigated by introducing an intermediate melting
the successful joining of dissimilar alloys. temperature alloy. Similar to the characteristics difference
To better understand these challenges, Reichardt et al. of dissimilar melting temperature, CTE, and thermal
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noted that most dissimilar joining issues can be grouped conductivity play a significant role in the interfacial
into three distinct categories: (i) Intermetallic formation bonding region of the bimetallic structures. Regarding
and solubility limitations, (ii) thermal property mismatch, CTE, thermal mismatch can result in an unequal thermal
and (iii) other metallurgical effects. In Section 3, which contraction, leading to a stress concentration at the
focuses on the interfacial characteristics of the discrete interface. The disparity of thermal conductivity could cause
MMAM structure, the aforementioned phenomena can be distortion and a lack of complete fusion of the low thermal
observed. Many of these issues have been resolved in the conductivity material due to insufficient heat present. In
welding industry through effective practice of introducing Section 3, a detailed description of the bimetallic structures
filler metals, interlayer blazing, high energy density beam that were analyzed using EDS, electron backscatter
welding, and friction stir welding. 42,106-108 The three main diffraction, and X-ray diffraction to understand the alloy
categories of joining issues and strategies to overcome compatibility at the abrupt change in element composition
each will be examined in more detail. From those, the in discrete MMAM is presented.
formation of brittle intermetallic phases in dissimilar
alloys is the biggest challenge in the MMAM process. 2.6. Powder recyclability and reuse
Most metal alloys have limitations in solid solubility and Powder reuse presents complex challenges due to the
tend to form ordered intermetallic phases. This becomes diverse thermal properties, oxidation susceptibility, and
more complex when considering commercial alloys chemical reactivity of the constituent alloys. These factors
with multiple elements, including impurities that could critically affect process stability, part performance, and
lead to detrimental phases. In cases of Ti/steel or Ti/Ni reproducibility. In powder-based metal AM processes
alloys (Sections 3.1, 3.2, and 3.3 for more explanation), such as LPBF, EB-PBF, and LDED, powder degradation
which tend to form brittle intermetallic approaches such is influenced by its interaction with high-energy sources
as introducing a third dissimilar metal alloy that acts as (e.g., laser and electron beam), molten metal, ambient

Volume 1 Issue 2 (2025) 7 doi: 10.36922/ESAM025180010