Harnessing Bifunctional Nitrogen-Dislocation Interactions for a Record Ultra-Strong-and-Ductile Duplex Titanium Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Duplex titanium (Ti) alloys exhibit limited uniform elongation due to insufficient work hardening and strain incompatibility.
• Interstitial atoms like nitrogen (N) and oxygen (O) can negatively impact the strength-ductility balance in Ti alloys.

Purpose of the Study:

• To overcome the strength-ductility trade-off in duplex Ti alloys.
• To harness bifunctional nitrogen-dislocation interactions for enhanced mechanical properties.
• To engineer a heterogeneous lamella structure in a Ti-Cr-Zr-Al alloy.

Main Methods:

• Utilizing nitrogen (N) as a primary strengthening element.
• Designing a duplex Ti-Cr-Zr-Al alloy with a specific heterogeneous lamella microstructure.
• Investigating the interactions between nitrogen atoms and dislocations.

Main Results:

• Achieved ultrahigh yield strength (≈1532 MPa) and tensile strength (≈1869 MPa).
• Obtained significant uniform elongation (εu ≈10.2%) through the emission of dislocations.
• Demonstrated the formation of N-rich low-angle grain boundaries (LAGBs) and coherent interstitial-N α'-nanotwinned martensites.

Conclusions:

• Bifunctional nitrogen-dislocation interactions are key to constructing unique microstructures.
• The developed heterogeneous lamella structure enables simultaneous ultrahigh strength and large ductility in Ti alloys.
• This strategy offers a new pathway for designing advanced interstitial-strengthening Ti alloys.