Spinodal-modulated solid solution delivers a strong and ductile refractory high-entropy alloy

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Body-centered-cubic (BCC) refractory high-entropy alloys (RHEAs) show promise for high-temperature applications, outperforming superalloys.
• A key challenge for BCC RHEAs is their lack of room-temperature tensile ductility and processability.
• Previous attempts to improve ductility by managing dislocation movement have sometimes led to embrittlement.

Purpose of the Study:

• To develop a new strategy for achieving ductile BCC HfNbTiV refractory high-entropy alloys.
• To overcome the inherent trade-off between high strength and ductility in RHEAs.
• To enhance the room-temperature processability of RHEAs.

Main Methods:

• Utilized spinodal decomposition to transform the BCC phase into a dual BCC arrangement (β(BCC1) + β*(BCC2)).
• Engineered nanometer-scale chemical composition modulations and elastic strain fields.
• Investigated the effect of these nanostructures on dislocation motion and plastic deformation mechanisms.

Main Results:

• Achieved a simultaneous combination of high yield strength (1.1 GPa) and tensile strain to failure (28%).
• The spinodally decomposed structure created significant lattice distortion, impeding dislocation movement.
• Observed enhanced strain hardening and delocalized plastic strain due to dislocation interactions and accumulation.

Conclusions:

• The spinodal decomposition strategy effectively enhances both strength and ductility in BCC RHEAs.
• Nanoscale structural engineering is a viable approach to overcome ductility limitations in refractory high-entropy alloys.
• The achieved properties represent a significant advancement for RHEAs in high-temperature and structural applications.