Innovative Design Approach Enhances Fatigue Resistance in Multi-Principal Element Alloys

Through precise control of the Cr/Ni ratio, the researchers synthesized two single-phase face-centered cubic (FCC) MPEAs with distinct stacking fault energies (SFEs).

Researchers at the Indian Institute of Science (IISc) Bangalore have developed a novel approach to designing fatigue-resistant multi-principal element alloys (MPEAs), offering new possibilities for advanced structural applications and further research into complex alloy systems. This breakthrough challenges conventional beliefs about the trade-off between strength and fatigue life, demonstrating how microstructural engineering can enhance material performance.

MPEAs are a unique class of materials composed of multiple principal elements rather than being dominated by one or two. Traditionally, it has been assumed that increasing strength through compositional modifications or the incorporation of brittle phases would negatively impact fatigue life. However, Dr. Ankur Chauhan and his team from the Department of Materials Engineering at IISc systematically investigated two critical microstructural features that enhance low-cycle fatigue (LCF) performance in the Cr-Mn-Fe-Co-Ni alloy system.

Through precise control of the Cr/Ni ratio, the researchers synthesized two single-phase face-centered cubic (FCC) MPEAs with distinct stacking fault energies (SFEs). Their findings revealed that the low-SFE alloy exhibited a 10–20% higher cyclic strength compared to the high-SFE alloy while maintaining a comparable fatigue life. This improvement is attributed to a delayed evolution of dislocation substructures and a reduced crack propagation rate in the low-SFE alloy.

Beyond single-phase alloys, the team engineered a dual-phase alloy that demonstrated an even greater enhancement—achieving a 50–65% increase in cyclic strength over the single-phase low-SFE alloy while preserving a similar fatigue life. The superior fatigue resistance of the dual-phase alloy stems from a combination of factors, including finer dislocation structures, increased back stresses due to refined grain sizes, crack deflection by brittle sigma (σ) precipitates, and extensive deformation twinning around fatigue cracks that complement slip activity and slow crack propagation.

These findings establish a framework for designing both single-phase and dual-phase fatigue-resistant MPEAs, with significant implications for structural applications in industries such as aerospace, automotive, and energy. By providing deeper insights into deformation and damage mechanisms, this research enhances the understanding of how SFE and secondary brittle phases influence the mechanical properties of MPEAs. This study is supported by the Anusandhan National Research Foundation, a statutory body under the Government of India, reinforcing the nation’s commitment to advancing materials science and engineering.

With these advancements, the study paves the way for further exploration into complex alloy systems, potentially leading to next-generation materials that combine high strength with exceptional fatigue resistance for demanding applications.