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<p>Residual stresses in additively manufactured iron-chromium-aluminum (Fe-Cr-Al) alloys, a leading candidate for accident-tolerant nuclear cladding, critically influence structural reliability yet remain challenging to quantify accurately. Conventional approaches such as x-ray diffraction (XRD) provide elastic residual stress measurements but are limited by surface sensitivity, texture effects, and experimental complexity. In this study, nanoindentation-based residual stress evaluation in LPBF-processed Fe-Cr-Al was investigated using XRD as a reference framework. XRD result confirmed a single-phase body-centered cubic (BCC) structure and revealed a Type I residual stress magnitude of 420 ± 2&#xa0;MPa in the as-printed condition, which was substantially reduced after heat treatment to 181 ± 52&#xa0;MPa. Nanoindentation, performed with 18 indents per condition, yielded comparable residual stress values for the AP state (459 ± 188&#xa0;MPa, using H850 as a reduced-stress reference condition), showing consistency in mean residual stress magnitude and compressive nature relative to XRD measurements. Distinct pileup morphologies around Berkovich imprints reflected the stress state, with three-sided pileup associated with high compressive stress in AP and asymmetric two-sided pileup consistent with stress relaxation in H850. Tensile testing established the macroscopic consequences of residual stress evolution, with the AP condition exhibiting higher yield and ultimate tensile strength, while the stress-relieved H850 condition showed enhanced ductility. Taken together, these results demonstrate trend-level consistency between nanoindentation-derived stress estimates and XRD-based residual stress measurements in LPBF Fe-Cr-Al alloys and highlight nanoindentation as a practical, localized, and scalable approach for linking residual stress to mechanical performance in LPBF-processed ferritic Fe-Cr-Al alloys relevant to advanced nuclear applications.</p>

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Exploring Nanoindentation-Based Residual Stress Evaluation in Laser Powder Bed Fusion Fe-Cr-Al Alloys with x-ray Diffraction Reference

  • 期刊论文

  • 发表日期：

    2026年6月18日

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  • Dan T. Nguyen,
  • Madhavan Radhakrishnan,
  • Reza Mirshams,
  • Narendra Dahotre,
  • Soumya Srotaswini Sahoo,
  • Bibhudutta Rout

摘要

Residual stresses in additively manufactured iron-chromium-aluminum (Fe-Cr-Al) alloys, a leading candidate for accident-tolerant nuclear cladding, critically influence structural reliability yet remain challenging to quantify accurately. Conventional approaches such as x-ray diffraction (XRD) provide elastic residual stress measurements but are limited by surface sensitivity, texture effects, and experimental complexity. In this study, nanoindentation-based residual stress evaluation in LPBF-processed Fe-Cr-Al was investigated using XRD as a reference framework. XRD result confirmed a single-phase body-centered cubic (BCC) structure and revealed a Type I residual stress magnitude of 420 ± 2 MPa in the as-printed condition, which was substantially reduced after heat treatment to 181 ± 52 MPa. Nanoindentation, performed with 18 indents per condition, yielded comparable residual stress values for the AP state (459 ± 188 MPa, using H850 as a reduced-stress reference condition), showing consistency in mean residual stress magnitude and compressive nature relative to XRD measurements. Distinct pileup morphologies around Berkovich imprints reflected the stress state, with three-sided pileup associated with high compressive stress in AP and asymmetric two-sided pileup consistent with stress relaxation in H850. Tensile testing established the macroscopic consequences of residual stress evolution, with the AP condition exhibiting higher yield and ultimate tensile strength, while the stress-relieved H850 condition showed enhanced ductility. Taken together, these results demonstrate trend-level consistency between nanoindentation-derived stress estimates and XRD-based residual stress measurements in LPBF Fe-Cr-Al alloys and highlight nanoindentation as a practical, localized, and scalable approach for linking residual stress to mechanical performance in LPBF-processed ferritic Fe-Cr-Al alloys relevant to advanced nuclear applications.