image: Solid PFZ as Electrolyte
Credit: Mingze Wang, Yongfeng Shen and Nan Jia from Northeastern University.
A group of researchers from Northeastern University of China developed a novel FeCrVNiAl eutectic high-entropy alloys (EHEA) that exhibits a remarkable combination of mechanical strength and high corrosion resistance for marine environments. The alloy integrates hierarchical nanoscale precipitates of B2 (NiAl) and L21 (Fe2CrV) phases within its matrix, which are precisely controlled through solid solution and aging treatments. These precipitates induce multistage strengthening mechanisms, including dislocation interactions, strain hardening, and the formation of misfit dislocations at coherent interfaces. The result is an alloy capable of bearing compressive stresses up to ~3.05 GPa, while simultaneously maintaining outstanding ductility and strain-hardening capabilities. Additionally, the microstructure promotes the formation of a stable passive film comprising chromium oxide, which reduces corrosion current density and enhances resistance in saline, marine-like environments. This dual achievement addresses a key challenge faced by traditional marine materials, which often fail in harsh conditions either by lacking sufficient strength or corrosion resistance. The study offers a new microstructural design that not only achieves these demanding properties but also provides insights into the underlying mechanisms contributing to this synergy.
The durability and safety of marine infrastructure depend heavily on materials capable of withstanding extreme mechanical stresses while resisting corrosion in aggressive saline environments. Currently, austenitic steels and low-carbon steels are widely used but are limited by their low strength and susceptibility to corrosion-induced degradation. Although high-entropy alloys (HEAs) have garnered significant attention due to their excellent mechanical properties and potential for tailor-made microstructures, existing solutions often involve trade-offs between strength and corrosion resistance. For example, traditional HEAs tend to suffer from elemental segregation, which weakens their plasticity and increases vulnerability to corrosion. Eutectic HEAs (EHEAs), composed of alternating lamellar phases, have shown promise owing to their unique microstructures, but achieving a balanced combination of ultrahigh strength and corrosion resistance remains a challenge. The formation of nanostructured precipitates within these alloys is known to enhance mechanical performance significantly; however, designing microstructures that simultaneously promote corrosion resistance and high strength in marine environments has remained elusive.
The Solution: The researchers from Northeastern University of China reported a new class of Fe30Cr15V15Ni20Al20 eutectic HEAs with multistage precipitations with a high mechanical strength and corrosion resistance for in marine environments. . By alloying Fe, Cr, V, Ni, and Al in a eutectic composition, the researchers created a microstructure featuring hierarchical nanosized precipitates of B2 NiAl and L21 Fe2CrV phases embedded within a BCC matrix. The multistage precipitations are achieved through controlled solid solution and aging treatments, leading to a uniform distribution of nanoscale particles that effectively retard dislocation motion and promote strain hardening. Notably, the presence of coherent interfaces with low elastic misfit between different phases facilitates the formation of dislocations, which further delay crack initiation and propagation. These microstructural features result in an extraordinary yield strength of ~2.33 GPa, ultimate compressive strength of ~3.05 GPa and a strain of 28 ± 2 %. Simultaneously, the alloy exhibits stable passive film formation predominantly composed of chromium oxide, reducing corrosion currents (6.42 mA·cm-2) and ensuring long-term corrosion resistance in saline conditions typical of marine environments. The combined mechanical reinforcement and corrosion protection demonstrate the potential of this microstructural engineering approach for robust, high-performance marine materials.
The Future: While the current results are highly promising, further efforts are required to optimize the alloy's microstructure for practical applications. Future research may focus on refining the aging process to control precipitate size and distribution further, aiming to enhance ductility without compromising strength. Investigations into scalable manufacturing processes such as casting and thermomechanical treatments are essential to facilitate industrial adoption. Additionally, comprehensive testing under real marine conditions, including long-term corrosion assessments, fatigue behaviour, and mechanical property evaluations at different temperatures and loading modes, will be vital to confirm the alloy’s performance in operational environments. Exploring the potential for alloying variations to improve properties such as impact toughness, fracture toughness, and weldability could expand its applicability.
The Impact: This work offers a promising pathway to achieve ultrahigh compressive strength combined with excellent anti-corrosion performances for marine drilling platform and introduces innovative concept of multistage precipitations in eutectic high-entropy alloys.
The research has been recently published in the online edition of Materials Futures, a prominent international journal in the field of interdisciplinary materials science research.
Reference:Mingze Wang, Yongfeng Shen, Nan Jia, Wenying Xue, Xinli Wang. Multistage precipitation triggering 3 GPa compressive strength and superior corrosion resistance in a FeCrVNiAl alloy[J]. Materials Futures, 2025, 4(3): 035004. DOI: 10.1088/2752-5724/adf2c1
Journal
Materials Futures