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Materials Science in Additive Manufacturing Heterostructures of A131 steel by DED

In this study, A131 steel with heterostructures, 2.2. Fabrication process
comprising alternating layers of coarse and fine grains, was The AB A131 EH36 steel used in this study was fabricated
successfully developed using a DED method that utilizes using a DED AM machine (Figure 2A) equipped with
the dendritic growth features of melt pools and thermal a fiber laser (wavelength: 1070 nm; laser beam spot
cycle behavior. An HT and commercial hot-rolled (HR) diameter: 2.5 mm) under an argon atmosphere (1 bar
A131 steel was also employed in this study as the control pressure). The DED settings were: 1.23 kW laser power,
group. The tensile strength of the AB A131 steel exhibited 0.5 mm layer thickness, 1200 mm/min moving speed,
an exceptional combination of strength, approaching that 1.25 mm track space, and 722.2 mm/min powder feeding
of Ti64 alloy, and plasticity within the range specified speed with Gaussian distribution. The orthogonal strategy
by the ductile ASTM A131 standard. To understand the was used, where the moving direction rotated by 90° for
formation mechanism of the heterostructure, multitype each alternating layer alongside the building direction
microstructure characterization and single-pass deposition (Figure 2B). To distinguish the building direction, a 3D
experiments were employed to elucidate the model of the axis was constructed with normal direction (ND; parallel
alternating layer of fine and coarse grains with crystal to the laser deposition), transverse direction (TD), and
misorientation. In addition, molecular dynamics (MD) was rolling direction (RD).
employed to reconstruct the model of the heterogeneous
microstructure according to the observed microstructure. In the HT process, the AB A131 EH36 steel was
The model was stretched in the same direction as the quenched and subsequently tempered using a box-type
experimental process to reveal the anisotropy of the tensile furnace (MXQ1600-40, MICRO-X Ltd Co., China)
behavior of the AB A131 steel. This innovative structural (Figure 2C). The cleaned AB A131 EH36 bulk was heated
design strategy presents a promising insight into crafting (10 K/min) at 910°C for 0.5 h, followed by water quenching,
traditional iron with a remarkable strength-plasticity subsequent tempering at 500°C for 2 h (Figure 2D), and
combination free from trade-off effects, with broader air-cooling. To investigate the formation mechanism of
implications for other conventional alloys in the industries. the microstructure, single-pass deposition of A131 steel
was carried out using the DED method with the same
2. Materials and methods parameters.
2.1. Materials 2.3. Material characterization

In this study, commercial gas-atomized mild steel powders The starting raw materials and bulks were characterized
(A131 EH36; particle size: 45 – 90 µm; Zhongyuan using a scanning electron microscope (SEM) (JEOL
Advanced Materials Technology Co., Ltd, China) were JSM-5500LV; JEOL Ltd., Japan) equipped with an
utilized (Figure 1A). The powder was approximately energy-dispersive X-ray spectrometer (EDS). The
spherical, with a low-carbon equivalent value (0.3%) microstructure of the bulks was also examined using an
(Figure 1B; Table S1). For comparison, commercial HR SEM system (Apreo 2 SEM; Thermo Fisher Scientific,
A131 steel bulk (ThyssenKrupp Material Services GmbH United States of America [USA]) equipped with EDS and
Co., Ltd., Germany) was used as the control group. All an electron backscatter diffraction (EBSD) detector. The
materials were used in the as-received state. microstructure was also observed using a laser confocal

A B

Figure 1. Steel powder morphology (A) and elemental composition (B)

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