Highly stable coherent nanoprecipitates via diffusion-dominated solute uptake and interstitial ordering.

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• High-strength aluminum (Al) alloys are crucial for lightweight design and advanced energy applications.
• Current commercial Al alloys are limited to applications below 150°C due to challenges in achieving thermally stable, high-volume fraction coherent nanoprecipitates.
• This limitation stems from the difficulty in combining slow-diffusing solutes (for stability) and fast-diffusing solutes (for volume fraction).

Purpose of the Study:

• To develop high-strength Al alloys capable of operating at 300–400°C.
• To overcome the limitations of current Al alloys by creating stable, coherent nanoprecipitates at high temperatures.
• To investigate a novel interstitial solute stabilizing strategy for Al-Cu-Mg-Ag alloys.

Main Methods:

• Development of Sc-added Al-Cu-Mg-Ag alloys.
• Utilizing an interstitial solute stabilizing strategy to form coherent nanoprecipitates (V phase).
• Investigating the formation mechanism of the V phase via coherent ledge-aided in situ phase transformation.

Main Results:

• Achieved high-density, highly stable coherent nanoprecipitates (V phase) in Sc-added Al alloys.
• Demonstrated unprecedented creep resistance and exceptional tensile strength (~100 MPa) at 400°C.
• Identified the formation mechanism involving slow-diffusing Sc and fast-diffusing Cu atoms, facilitated by ledge-mediated interactions.

Conclusions:

• The interstitial solute stabilizing strategy enables the creation of stable coherent nanoprecipitates for high-temperature Al alloys.
• Ledge-mediated interactions between slow- and fast-diffusing atoms are key to stabilizing nanoprecipitates.
• This approach paves the way for advanced 400°C-level light alloys suitable for industrial production.