Nitrogen-Containing High-Entropy Alloy Reveals Temperature-Shaped Microstructural Recovery

A laboratory study of an as-cast nitrogen-containing high-entropy alloy shows that its microstructural response during hot deformation changes sharply with temperature, even though the alloy’s flow stress does not fall in a simple, step-by-step manner. Researchers investigated Fe46Mn35.5Co9Cr9N0.5 at.% alloy through isothermal compression tests conducted from 700 to 1000 °C at a strain rate of 0.001 s−1. The material displayed a pronounced decrease in peak flow stress as temperature increased, together with a relatively high peak strain of approximately 0.4 and limited post-peak softening.

The central finding is that dynamic recrystallization could begin well below the stress and strain levels associated with the peak of the deformation curve. Poliak–Jonas analysis indicated that the restoration process started at stresses and strains far below the measured peak values, while the final microstructure contained a significant fraction of recrystallized grains. This distinction matters because the onset of recrystallization did not automatically produce a dominant macroscopic softening response. Instead, the alloy’s behavior reflected a sustained competition between the storage of dislocations and mechanisms that restore, or reorganize, the deformed structure.

At 700 °C, the deformation structure was dominated by extended dynamic recovery, accompanied by localized evidence of continuous dynamic recrystallization, or cDRX. The researchers associated this state with elongated grains, serrated grain boundaries and dense networks of low-angle boundaries. In practical terms, the alloy was simultaneously retaining deformation-related defects and developing localized regions of new grain formation. The limited reduction in flow stress beyond the peak strain is consistent with the idea that recovery and dislocation storage continued to operate strongly at this temperature, tempering the expected macroscopic effect of the localized recrystallization.

At 900 °C, advanced cDRX became the more important restoration mechanism, producing extensive grain refinement and a larger population of fine, equiaxed recrystallized grains. The study also recorded an unusual intragranular necklace-like arrangement and abundant Σ3 annealing twins. These features indicate a more extensive reorganization of the alloy’s microstructure than was observed at the lower temperature. Across the tested range, the work demonstrates that reaching conditions favorable for dynamic recrystallization is not the same as observing a large drop in flow stress: at lower temperature, recovery and dislocation storage remained predominant alongside localized cDRX, whereas at 900 °C, substantially greater cDRX development accompanied pronounced grain refinement and flow softening. The study concerns hot-deformation behavior in a specific as-cast alloy composition and testing protocol, so its results describe the mechanisms observed under those conditions rather than universal behavior for all high-entropy alloys.

Subject of Research: Temperature-dependent hot-deformation and microstructural restoration mechanisms in an as-cast Fe–Mn–Co–Cr high-entropy alloy

Article Title: Temperature-dependent microstructural stability and dynamic restoration mechanisms in an as-cast nitrogen-containing Fe–Mn–Co–Cr high-entropy alloy

Article References: Shamouni, Y., Zarei-Hanzaki, A., Ghorbani, M., Tajik, A., Moshiri, A., Abbasi, A., Park, H., Kim, H. S., & Abedi, H. R. (2026). Temperature-dependent microstructural stability and dynamic restoration mechanisms in an as-cast nitrogen-containing Fe–Mn–Co–Cr high-entropy alloy. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13702-y

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DOI: 10.1007/s10853-026-13702-y

Keywords: high-entropy alloys, nitrogen-containing alloys, hot deformation, dynamic recovery, continuous dynamic recrystallization, microstructural stability, grain refinement, annealing twins, flow stress, Temperature-dependent, microstructural, stability