Enhanced strength of A131 steel via heterostructures induced by laser-directed energy deposition

The trade-off between strength and plasticity has posed a challenge to the broader application of conventional metallic structural materials in high-speed, heavy-load, and extreme service environments. Heterogeneous structure designs could potentially overcome these limitations with their inherent superior combination of strength and plasticity. To harness this potential, this study employed a directed energy deposition additive manufacturing (AM) technology to fabricate a novel heterostructure in as-built (AB) A131 steel, consisting of alternating coarse and fine-grain layers along the building direction. In addition, a heat treatment process was applied to fabricate a near-homogeneous microstructure, allowing for the investigation of the role of crystal misorientation in tensile anisotropy. Compared to the performance of commercial hot-rolled ASTM A131 steel (yield strength [σYS]: 346.5 MPa; ultimate tensile strength [σUTS]: 545.0 MPa), the AB A131 steel achieved significant enhancements of 168.3% and 78.0% in σYS and σUTS, respectively, when maintaining a comparable elongation of 24.6% along the deposition direction similar to the ASTM A131 standard. Comprehensive experimental characterizations, combined with molecular dynamics simulations, were conducted to investigate the underlying formation mechanism of the heterostructure and the origins of mechanical anisotropy. It was found that single-pass deposition produced three distinct microstructure regions with different grain sizes owing to dendrite growth. With repeated thermal cycles, these evolved into a layered heterostructure consisting of alternating fine crystals and coarse-columnar grains. This heterostructure remarkably contributed to an exceptional improvement in strength, accompanied by only a minor reduction in plasticity. These findings present an efficacious avenue for substantially augmenting the mechanical properties of conventional iron-based alloys, offering useful references for overcoming the strength-plasticity trade-off in other alloys fabricated by AM.

- Kuntanapreeda S, Hess D. Opening access to space by maximizing utilization of 3D printing in launch vehicle design and production. Appl Sci Eng Prog. 2021;14(2):143-145. doi: 10.13316/j.asep/2020/12.002
- Liu S, Shin YC. Additive manufacturing of Ti6Al4V alloy: A review. Mater Des. 2019;164:107552. doi: 10.1016/j.matdes.2018.107552
- Liu TS, Chen P, Qiu F, et al. Review on laser directed energy deposited aluminum alloys. Int J Extreme Manuf. 2024;6(2):022004. doi: 10.1088/2631-7990/ad16bb
- Zhang B, Gao Z, Xiao H, Yang X, Li Y, Zhu H. Size effects and optimization during laser directed energy deposition on high thermal conductivity copper alloys. J Mater Res Technol. 2024;33:4389-4399. doi: 10.1016/j.jmrt.2024.10.104
- Bai Y, Chaudhari A, Wang H. Investigation on the microstructure and machinability of ASTM A131 steel manufactured by directed energy deposition. J Mater Process Technol. 2020;276:116410. doi: 10.1016/j.jmatprotec.2019.116410
- Gu D, Shi X, Poprawe R, Bourell DL, Setchi R, Zhu J. Material-structure-performance integrated laser-metal additive manufacturing. Science. 2021;372(6545):eabg1487. doi: 10.1126/science.abg1487
- Seedhouse E, editor. Falcon 9 and falcon heavy. In: SpaceX: Starship to Mars The First 20 Years. New York: Springer International Publishing; 2022. p. 71-93.
- Materials ASfTa. ASTM A131/A 131M-04. Standard Specification for Structural Steel for Ships. Commonwealth of Pennsylvania: ASTM International; 2004.
- Sirisatien T, Mahabunphachai S, Sojiphan K. Effect of submerged arc welding process with one-side one-pass welding technique on distortion behavior of shipbuilding steel plate ASTM A131 grade A. Mater Today Proc. 2018;5(3, Part 2):9543-9551. doi: 10.1016/j.matpr.2017.10.136
- Yan Q, Chen B, Kang N, et al. Comparison study on microstructure and mechanical properties of Ti-6Al-4V alloys fabricated by powder-based selective-laser-melting and sintering methods. Mater Charact. 2020;164:110358. doi: 10.1016/j.matchar.2020.110358
- Yan Q, Chen B, Jia Z, et al. Formation of dual quasi-continuous networked structure and its strengthening effect in Ti-6Al-4V alloy reinforced with graphene via powder bed fusion. Add Manuf. 2024;92:104364. doi: 10.1016/j.addma.2024.104364
- Bai Y, Yan Y, Chen J, Liang C, Bi G, Zhao C. Microstructure and mechanical property evolution of 316L/18Ni300 bimetallic structure manufactured by laser powder bed fusion. Mater Sci Eng A. 2025;929:148141. doi: 10.1016/j.msea.2025.148141
- Ang LJJ, Huang J, Nai MLS, Wang P. Additive manufacturing techniques for EH36 steels: Challenges and future directions. ESAM. 2025;1(1):025060005. doi: 10.36922/esam025060005
- Wenjin W, Beng TS, Kai CC, et al. Preliminary investigation on SLM of ASTM A131 EH36 high tensile strength steel for shipbuilding applications. Proceedings of the 2nd International Conference on Progress in Additive Manufacturing; 2014. doi: 10.3850/978-981-09-0446-3_083
- Wu W, Tor SB, Merchant AA. Tensile properties of ASTM A131 EH36 shipbuilding steel processed by selective laser melting. Proceedings of the 3rd International Conference on Progress in Additive Manufacturing; 2018.
- Wang J, Wu WJ, Jing W, et al. Improvement of densification and microstructure of ASTM A131 EH36 steel samples additively manufactured via selective laser melting with varying laser scanning speed and hatch spacing. Mater Sci Eng A. 2019;746:300-313. doi: 10.1016/j.msea.2019.01.019
- Wang J, Chew YX, Wu WJ, et al. Microstructure and mechanical properties of ASTM A131 EH36 steel fabricated by laser aided additive manufacturing. Mater Charact. 2021;174:110949. doi: 10.1016/j.matchar.2021.110949
- Wang J, Zhang M, Wang B, et al. Influence of surface porosity on fatigue life of additively manufactured ASTM A131 EH36 steel. Int J Fatigue. 2021;142:105894. doi: 10.1016/j.ijfatigue.2020.105894
- Liu L, Li S, Pan D, et al. Loss-free tensile ductility of dual-structure titanium composites via an interdiffusion and self-organization strategy. Proc Natl Acad Sci U S A. 2023;120(28):e2302234120. doi: 10.1073/pnas.2302234120
- Gao S, Li Z, Van Petegem S, et al. Additive manufacturing of alloys with programmable microstructure and properties. Nat Commun. 2023;14(1):6752. doi: 10.1038/s41467-023-42326-y
- Tan C, Li R, Su J, et al. Review on field assisted metal additive manufacturing. Int J Mach Tools Manuf. 2023;189:104032. doi: 10.1016/j.ijmachtools.2023.104032
- Svetlizky D, Das M, Zheng B, et al. Directed energy deposition (DED) additive manufacturing: Physical characteristics, defects, challenges and applications. Mater Today. 2021;49:271-295. doi: 10.1016/j.mattod.2021.03.020
- Kong H, Yibo L, Fuxiang L, et al. In situ fabrication of martensitic stainless steel via heterogeneous double-wire arc-directed energy deposition. Virt Phys Prototyp. 2024;19(1):e2350610. doi: 10.1080/17452759.2024.2350610
- Myers MB, Bandyopadhyay A. Understanding the antibacterial efficacy of additively manufactured copper-added 316L stainless steel. MSAM. 2025;4(1):7357. doi: 10.36922/msam.7357
- Zuckschwerdt NW, Bandyopadhyay A. Multi-material structures of Ti6Al4V and Ti6Al4V-B4C through directed energy deposition-based additive manufacturing. MSAM. 2024;3(3):3571. doi: 10.36922/msam.3571
- Su J, Li Q, Teng J, et al. Programmable mechanical properties of additively manufactured novel steel. Int J Extreme Manuf. 2025;7(1):015001. doi: 10.1088/2631-7990/ad88bc
- Dan X, Ren C, Song Z, et al. Exceptional strength and ductility in heterogeneous multi-gradient TiAl alloys through additive manufacturing. Acta Mater. 2024;281:120395. doi: 10.1016/j.actamat.2024.120395
- Wu X, Yang M, Yuan F, et al. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility. Proc Natl Acad Sci U S A. 2015;112(47):14501-14505. doi: 10.1073/pnas.1517193112
- Li D, Fan G, Huang X, et al. Enhanced strength in pure Ti via design of alternating coarse- and fine-grain layers. Acta Mater. 2021;206:116627. doi: 10.1016/j.actamat.2021.116627
- Tan C, Li Q, Yao X, et al. Machine learning customized novel material for energy-efficient 4D printing. Adv Sci. 2023;10(10):2206607. doi: 10.1002/advs.202206607
- National Standardization Administration of the People’s Republic of China. GB/T 36165-2018. Determination of Average Grain Size of Metal -- Electron Backscatter Dirffraction (EBSD) Method. Beijing: National Standardization Administration of the People’s Republic of China; 2018.
- Plimpton S. Fast parallel algorithms for short-range molecular dynamics. J Comput Phys. 1995;117(1):1-19. doi: 10.1006/jcph.1995.1039
- Zhan JM, Yao XH, Han F. An approach of peridynamic modeling associated with molecular dynamics for fracture simulation of particle reinforced metal matrix composites. Compos Struct. 2020;250:112613. doi: 10.1016/j.compstruct.2020.112613
- Proville L, Choudhury A. Unravelling the jerky glide of dislocations in body-centred cubic crystals. Nat Mater. 2024;23(1):47-51. doi: 10.1038/s41563-023-01728-5
- Etesami SA, Asadi E. Molecular dynamics for near melting temperatures simulations of metals using modified embedded-atom method. J Phys Chem Solids. 2018;112:61-72. doi: 10.1016/j.jpcs.2017.09.001
- Lim H, Hale LM, Zimmerman JA, Battaile CC, Weinberger CR. A multi-scale model of dislocation plasticity in α-Fe: Incorporating temperature, strain rate and non-schmid effects. Int J Plastic. 2015;73:100-118. doi: 10.1016/j.ijplas.2014.12.005
- Vasques CMA, Cavadas AMS, Abrantes JCC. Technology overview and investigation of the quality of a 3D-printed maraging steel demonstration part. MSAM. 2025;4(2):025040002. doi: 10.36922/msam025040002
- Li W, Yan L, Chen X, Zhang J, Zhang X, Liou F. Directed energy depositing a new Fe-Cr-Ni alloy with gradually changing composition with elemental powder mixes and particle size’ effect in fabrication process. J Mater Proc Technol. 2018;255:96-104. doi: 10.1016/j.jmatprotec.2017.12.010
- Donizete Borba TM, Wagner DF, Leonardo DOT, Cardoso R Jr. Assessment of the weldability of EH36 TMCP shipbuilding steel welded by high heat input submerged arc welding. Weld Int. 2017;31(3):184-195. doi: 10.1080/09507116.2016.1218619
- Potez L, Lapasset G, Kubin L. Jerky flow (the PLC effect) in Ll2 Al3Ti-based alloys. Scr Metallurgica Mater. 1992; 26(5):841-846. doi: 10.1016/0956-716X(92)90449-O
- Hsu WC, Shen TE, Liang YC, Yeh JW, Tsai CW. In situ analysis of the portevin-le chatelier effect from low to high-entropy alloy in equal HfNbTaTiZr system. Acta Mater. 2023;253:118981. doi: 10.1016/j.actamat.2023.118981
- Ananthakrishna G. Current theoretical approaches to collective behavior of dislocations. Phys Rep. 2007; 440(4-6):113-259. doi: 10.1016/j.physrep.2006.10.003
- Sarkar A, Maloy SA, Murty KL. Investigation of portevin-le chatelier effect in HT-9 steel. Mater Sci Eng A. 2015;631:120-125. doi: 10.1016/j.msea.2015.02.022
- Vahedi Nemani A, Ghaffari M, Nasiri A. Comparison of microstructural characteristics and mechanical properties of shipbuilding steel plates fabricated by conventional rolling versus wire arc additive manufacturing. Add Manuf. 2020;32:101086. doi: 10.1016/j.addma.2020.101086
- Chen ZW, Phan MAL, Darvish K. Grain growth during selective laser melting of a co-cr-mo alloy. J Mater Sci. 2017;52(12):7415-7427. doi: 10.1007/s10853-017-0975-z
- Kok Y, Tan XP, Wang P, et al. Anisotropy and heterogeneity of microstructure and mechanical properties in metal additive manufacturing: A critical review. Mater Des. 2018;139:565-586. doi: 10.1016/j.matdes.2017.11.021