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Process parameter-dependent microstructure and strain hardening behaviour in L-PBF AISI 4340: Role of retained austenite

Lookup NU author(s): Dr Xinwei LiORCiD

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Abstract

© 2026 Elsevier B.V.Microstructure engineering of AISI 4340 steel via laser powder bed fusion (L -PBF) is demonstrated in this study as a route to achieving a tailored balance of strength, ductility, and strain hardening directly in the as-printed state. By systematically varying laser power and energy density, the influence of process-induced thermal histories on phase formation is examined, including the stabilization of retained austenite (RA) within a tempered martensitic matrix. Through combined experimental characterization and finite element thermal simulations, the presence of metastable RA is found to be associated with enhanced strain hardening via deformation-induced transformation. This enables tailoring of the yield strength (YS)-to-ultimate tensile strength (UTS) ratio (0.65–0.82). The best-performing sample achieves a UTS of 1747 MPa with elongation exceeding 10%, surpassing most reported L -PBF steels. The results indicate that process parameter selection in L -PBF can significantly influence the thermal history, microstructure, and mechanical response. These findings suggest that L -PBF processing provides a promising pathway for microstructure–property design in high-strength steels.

Publication metadata

Author(s): Tan YH, Cagirici M, Hu Z, Ong CYA, Willy HJ, Li X, Liang X, Sui S, Herng TS, Ding J, Wang P

Publication type: Article

Publication status: Published

Journal: Additive Manufacturing

Year: 2026

Volume: 124

Print publication date: 25/05/2026

Online publication date: 15/05/2026

Acceptance date: 13/05/2026

ISSN (print): 2214-8604

Publisher: Elsevier B.V.

URL: https://doi.org/10.1016/j.addma.2026.105241

DOI: 10.1016/j.addma.2026.105241

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