Coupling CALPHAD Method and Entropy-Driven Design for the Development of an Advanced Lightweight High-Temperature...

Area of Science:

• Materials Science
• Metallurgy
• Computational Materials Design

Background:

• Conventional aluminum alloys often lack the required high-temperature performance and strength for demanding applications.
• Developing advanced alloys with enhanced mechanical properties and thermal stability is crucial for technological progress.

Purpose of the Study:

• To develop a novel lightweight Al-Ti-Ta alloy with superior hardness and thermal stability.
• To investigate the effectiveness of combining CALPHAD methodology with entropy-driven design for alloy development.

Main Methods:

• CALPHAD (Calculation of Phase Diagrams) methodology for compositional optimization.
• Entropy-driven design principles for phase stabilization.
• Fabrication and isothermal heat treatment of the Al87.5Ti6.25Ta6.25 alloy.
• Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC).
• Nanomechanical property evaluation via nanoindentation and microhardness testing.

Main Results:

• A dual-phase microstructure consisting of an FCC matrix and an Al3(Ti,Ta)-type intermetallic phase was achieved.
• The FCC phase exhibited a high melting transition temperature of 660 °C.
• Exceptional microhardness of approximately 3300 MPa was recorded, surpassing conventional alloys like A390, 7075 Al, and CP-Ti.
• The alloy demonstrated superior specific strength compared to Ti-64 alloy at 15% lower density.
• Enhanced thermal stability was confirmed through prolonged heat treatment, attributed to entropy-driven phase stabilization.

Conclusions:

• The synergistic approach of CALPHAD and entropy-driven design is effective for developing advanced Al-based alloys.
• The developed Al-Ti-Ta alloy offers a promising combination of high hardness, thermal stability, and low density.
• This alloy presents a viable alternative to heavier or less performant conventional materials in high-temperature applications.