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Laser Additive Manufacturing of Zinc
A B

C

Figure 4. (A) The schematic of evaporation fumes and spatters. Reprinted from Journal of Materials Processing Technology, 258,
Wen P, Jauer L, Voshage M, et al., Densification behavior of pure Zn metal parts produced by selective laser melting for manufacturing
biodegradable implants, 128-137, Copyright (2018), with permission from Elsevier . (B) The evaporation fumes of Zn during LPBF.
[34]
Reprinted from Acta Biomaterialia, 98, Qin Y, Wen P, Guo H, et al., additive manufacturing of biodegradable metals: Current research status
and future perspectives, 3-22, Copyright (2019), with permission from Elsevier . (C) The dynamic X-ray images of liquid-solid powder
[35]
agglomeration spatter during LPBF. Reprinted from Additive Manufacturing, 36, Young Z A, Guo Q, Parab ND, et al., types of spatter and
their features and formation mechanisms in laser powder bed fusion additive manufacturing process, Copyright (2020), with permission
from Elsevier .
[76]
Epitaxial solidification is one special phenomenon, solidification theory . During solidification, the Zn
[88]
during which the crystallographic orientation depends grains may undergo different growth degrees, which
on that of the crystal grain on the base metal side of depend on the codirectionality degree of the preferred
[89]
the fusion line [85,86] . The crystals forming at the solid/ growth directions with the sharp heat gradient . As
liquid interface inherit the grain structure and crystalline shown in Figure 5A, a single track of laser scanning was
orientations of the previously solidified layer. Therefore, investigated. In these processing conditions, the growth

epitaxial solidification is caused by low undercooling rate of dendrite/cell along the growth direction v involves

sk
preceding the solidification front due to the repeated local the solidification front velocity v , which is related to the

s
melting and remelting of Zn-based materials, which is the thermal source velocity v , as described by :
[90]
energetically favorable mechanism for the columnar grain   sc ϕ = v cos  θ = v cos (2)
v
growth during LPBF . On the other hand, the formation s sk sc
[87]
of grain structure is decided by the thermal flow direction Where, the φ represents the angle between the
and solidification rate of metal materials according to preferred growth direction of Zn grains and unit direction
80 International Journal of Bioprinting (2022)–Volume 8, Issue 1