• • The GDS 304 stainless steel achieves ultra-high ratchetting resistance through a gradient dislocation structure with surface cell size of 290 nm and cell thickness of 50 nm, while maintaining a uniform grain size of 37 μm. This combination directly addresses the industrial need for dimensional stability in nuclear power pipelines and aircraft engines under long-term asymmetric cyclic loading.
• • Pre-torsion cyclic deformation generates a high density of low-angle boundaries in the surface region without altering grain morphology or crystallographic orientation, as confirmed by EBSD and TEM. This microstructural control prevents strain localization, a failure mode that limits conventional pre-strained coarse-grained metals to short-term cyclic service.
• • The material satisfies Lu's three criteria for high ratchetting resistance: high plastic strain hardening capacity, low dynamic recovery effect, and prevention of microstructural coarsening during cyclic deformation. These criteria provide a quantifiable design framework for next-generation fatigue-resistant alloys, moving beyond empirical composition tuning.
• • The GDS design overcomes the strength–ratchetting resistance trade-off observed in nanostructured metals and high-strength dual-phase steels, which typically exhibit reduced plastic hardening capacity and premature strain localization. This offers a scalable processing route for critical components requiring both high yield strength and long-term cyclic creep resistance.