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.

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

The study, titled “Microscopic insights into the mechanical behavior of a Ni-Co-based superalloy through in-situ neutron diffraction”, was published in Microstructures (Oct. 13, 2025).

“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.”

This work was supported by the National Key Research and Development Program of China (No. 2021YFA1600600), the National Natural Science Foundation of China (NSFC) (No. U2141206, 51921001), the Fundamental Research Funds for the Central Universities (Grant Nos. FRF-TP-20-03C2, FRF-BD-20-02B), and the Guangdong-Hong Kong-Macao Joint Laboratory for Neutron Scattering Science and Technology. The neutron diffraction experiments were conducted on the time-of-flight neutron diffractometer TAKUMI (BL 19) at the Materials and Life Science Experimental Facility of J-PARC under proposal No. 2020B0421.
DOI：10.20517/microstructures.2025.28