Schematic revealing strain-dependent mechanism transitions (shearing to Orowan looping) across different grains and the resulting evolution of dislocation types and configurations. Credit: Microstructures (2025). DOI: 10.20517/microstructures.2025.28

As the aerospace sector pursues propulsion systems that are cleaner, quieter, and more efficient, materials used in turbine components face increasingly demanding thermal and mechanical environments. Ni-Co-based superalloys are widely regarded as prime candidates for next-generation turbine disks due to their exceptional ability to retain strength under extreme temperature and stress.

Yet, a long-standing challenge has been pinpointing—at the microscopic scale—how these alloys sustain their strength during deformation, particularly regarding the interaction between dislocations and γ′ strengthening precipitates.

To address this challenge, a research team led by the University of Science and Technology Beijing (USTB) conducted in-situ neutron diffraction tensile experiments on an advanced Ni-Co-based superalloy using the TAKUMI engineering diffractometer at J-PARC.

The study, titled "Microscopic insights into the mechanical behavior of a Ni-Co-based superalloy through in-situ neutron diffraction," was published in Microstructures.

"It has been difficult to directly observe when dislocations cut through precipitates versus when they bypass them," the researchers note. "In-situ neutron diffraction enables real-time tracking of how load is partitioned between the γ matrix and γ′ precipitates as deformation proceeds."

"We identified a distinct transition in how the material resists deformation," said Dr. Yabo Liu, the first author.

"Initially, dislocations shear through the strengthening particles like a knife. But as deformation progresses, they switch to a ‘bypassing’ mechanism known as Orowan looping. This transition is crucial for the material’s load-bearing capacity."

The authors further connect this mechanism "relay" to evolving dislocation behavior. The alloy’s low stacking-fault energy suppresses cross-slip, increasing the proportion of screw dislocations.

Meanwhile, γ′ precipitates act as strong pinning sites, impeding dislocation self-organization into low-energy configurations and instead promoting high-energy, weakly screened dislocation arrangements—evidence consistent with planar-slip dominance in this class of alloys.

These findings also explain the alloy’s characteristic three-stage work-hardening response. The study associates the early-stage behavior with γ′ shearing, the mid-stage rise in hardening with the growing dominance of Orowan bypassing (evidenced by the separation of lattice strain between phases), and the late-stage decrease in hardening with localized, restricted cross-slip. This restricted cross-slip enables dislocations to bypass high-density obstacle regions formed by Orowan loops and accumulated dislocations.

"We have quantitatively linked precipitate-controlled mechanism transitions to load partitioning and dislocation configuration," said Prof. Shilei Li, a corresponding author from USTB.

"By resolving these microstructural responses, we can support more predictive modeling of work hardening and, ultimately, improve component performance in advanced disk superalloys."

More information: Yabo Liu et al, Microscopic insights into the mechanical behavior of a Ni-Co-based superalloy through in-situ neutron diffraction, Microstructures (2025). DOI: 10.20517/microstructures.2025.28

Provided by Frontiers Journals

Citation: Neutron diffraction unveils the ‘relay’ of hardening mechanisms in next-gen superalloys (2026, January 9) retrieved 9 January 2026 from https://techxplore.com/news/2026-01-neutron-diffraction-unveils-relay-hardening.html

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