A lightweight Fe–Mn–Al–C austenitic steel with ultra-high strength and ductility fabricated via laser powder bed fusion

Journal Article · 05 April 2023 · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing

DOI: https://doi.org/10.1016/j.msea.2023.145007 · OSTI ID:1972901

Seede, Raiyan ^[1]; Whitt, Austin ^[2]; Ye, Jiahui  ^[2]; Gibbons, Sean ^[3]; Flater, Philip  ^[4]; Gaskey, Bernard ^[4]; Elwany, Alaa ^[2]; Arroyave, Raymundo ^[2]; Karaman, Ibrahim  ^[2]

---

1. Texas A & M Univ., College Station, TX (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Materials Science Division
2. Texas A & M Univ., College Station, TX (United States)
3. Air Force Research Lab. (AFRL), Eglin Air Force Base, FL (United States). AFWERX
4. Air Force Research Lab. (AFRL), Eglin Air Force Base, FL (United States)

Lightweight Fe–Mn–Al–C steels have become a topic of significant interest for the defense and automotive industries. These alloys can maintain high strength and ductility while also reducing weight in structural applications. Conventionally processed Fe–Mn–Al–C austenitic steels with high Al content (~9 wt%) demonstrate greater than 1.5 GPa strength with 35% elongation. Several recent studies have demonstrated success in fabricating steel parts using laser powder bed fusion (L-PBF) additive manufacturing (AM), which can generate near-net-shape components with complex geometries and is capable of local microstructural control. However, studies on L-PBF processing of Fe–Mn–Al–C alloys have focused on low Al content (<5 wt%) compositional regimes representing alloys that undergo transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP). Here, in this study, we present the effects of L-PBF processing on the microstructure and mechanical properties of an Fe–30Mn–9Al–1Si-0.5Mo-0.9C austenitic steel. A process optimization framework is employed to determine an ideal L-PBF processing space that will result in >99% density parts. Implementing this framework resulted in near-fully dense specimens fabricated over a broad range of process parameters. Additionally, two bi-directional scan rotation strategies (90° and 67°) were applied to understand their effects on texture and anisotropy in this material. As-printed specimens displayed considerable work-hardening characteristics with average strengths of up to 1.3 GPa and 36% elongation in the build direction. However, solidification microcracks oriented in the build direction resulted in anisotropy in tensile strength and ductility resulting in average strengths of 1.1 GPa and 20% elongation perpendicular to the build direction. The successful L-PBF fabrication of Fe–30Mn–9Al–1Si-0.5Mo-0.9C presented here is expected to open new avenues for weight reduction in structural applications with a high degree of control over part topology.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); US Army Research Office (ARO); US Air Force Office of Scientific Research (AFOSR); National Science Foundation (NSF)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1972901
• Alternate ID(s): OSTI ID: 1971939
• Report Number(s): LLNL-JRNL-840862; 1062388
• Journal Information: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing, Journal Name: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing Vol. 874; ISSN 0921-5093
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English