Fatigue Properties of Ultrafine-Grained Metallic Materials

Ultrafine-grained (UFG) metallic materials, characterised by grain sizes typically below one micrometre, have garnered significant interest due to their enhanced strength, ductility and fatigue performance. By employing severe plastic deformation techniques such as equal channel angular pressing or high-pressure torsion, researchers achieve a refined microstructure with high dislocation density and a large grain boundary area. These microstructural features impede crack initiation and slow crack propagation, yielding improved low-cycle and high-cycle fatigue life in steels, aluminium alloys, copper and titanium. The global drive for lighter, stronger and more durable components in aerospace, automotive and biomedical sectors underpins the practical importance of UFG metals. Optimising grain size, boundary character and inclusion morphology has emerged as a unifying strategy to enhance fatigue strength, while retaining adequate toughness and corrosion resistance.

Research from Nature Portfolio

Recent studies have demonstrated that an α-Cu–15 at.% Al alloy processed by cold rolling followed by annealing to a moderate grain size of around 0.6 µm attains a fatigue strength approaching 280 MPa at ten million cycles. This performance exceeds that of its nanocrystalline counterpart despite a lower tensile strength, highlighting the importance of optimising grain size rather than maximising strength alone. A new “damage-reduction” strategy has been proposed, focusing on minimising initial microstructural defects and dispersing cyclic strain to delay crack nucleation. These findings establish a pathway for further improvements in fatigue performance across a broad range of high-strength alloys.

Fatigue Properties of Ultrafine-Grained Metallic Materials publication trend

The graph below shows the total number of articles in fatigue properties of ultrafine-grained metallic materials across all publications each year (not limited to Nature Index journals).

Technical terms

Ultrafine-grained (UFG) structure: A metallic microstructure with grain sizes below approximately 1 µm, produced by severe plastic deformation to enhance mechanical and fatigue properties.

Fatigue strength: The maximum cyclic stress amplitude a material can endure for a specified number of cycles without the onset of failure.

Low-cycle fatigue (LCF): Fatigue regime characterised by high plastic strain amplitudes and a relatively low number of cycles to failure, dominated by crack initiation processes.

High-cycle fatigue (HCF): Fatigue regime involving low stress amplitudes and a large number of cycles, where crack propagation kinetics govern life expectancy.

S–N curve: A plot of stress amplitude (S) versus number of cycles to failure (N) that defines the fatigue performance of a material under cyclic loading.

References

1. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size. Scientific Reports (2016).
2. The highest fatigue strength for steels. Acta Materialia (2025).
3. Effect of grain size on fatigue strength of 304 stainless steel. High Temperature Materials and Processes (2024).