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Materials Science in Additive Manufacturing Heterostructures of A131 steel by DED

A B

C D

Figure 11. Molecular dynamics (MD) simulation of the heterogeneous structure in AB A131 steel. (A) Model of the heterostructure. (B) Stress-strain curve
of the simulation. (C and D) Deformed model and strain mappings along (C) ND and (D) TD
Abbreviations: AB: As-built; ND: Nominal direction; TD: Transverse direction; BCC: Body centered cubic; RD: Roling direction

deformation primarily occurred in the fine-grain region. orientation along ND (Figures 3B and 7A), which also
This behavior contributed to the enhanced tensile strength resulted in significant grain disorientation (Figure S2)
and high plasticity, consistent with the experiment results and maintained tensile strength differences along different
of AB-ND. orientations.

Under tensile loading in TD, the deformed model 5. Conclusion
(Figure 11D) exhibited an irregular grain profile with
notable misorientation along TD. A significant necking This study demonstrated the formation of a heterostructure
phenomenon occurred, characterized by a narrow comprising alternative layers of coarse and fine grains
region where the primary shear strain was concentrated. in A131 steel fabricated using the DED technique and
This suggests uneven deformation and notable stress post-treatment processes. The structure featured notable
concentration, which facilitated premature crack initiation improvement in strength without the plasticity trade-off.
and propagation, ultimately reducing tensile strength and The phase configuration, heterogeneous microstructure,
elongation. Moreover, the stress concentration also limited and anisotropy in mechanical performance were thoroughly
the work-hardening capacity under constant loading, investigated, with comparisons made to commercial A131
consistent with the experimental AB-TD results. Even after steel. Finally, the formation of the heterostructure and the
HT, HT A131 steel retained the anisotropy performance as tensile performance were discussed based on the single-
tested along different directions, though the heterostructure pass deposition and MD simulation, respectively. The
disappeared. This can be attributed to the optimal crystal main conclusions were summarized as follows:

Volume 4 Issue 3 (2025) 12 doi: 10.36922/MSAM025220038