Lightweight TiVNb medium-entropy alloy with weak strength dependence on temperature

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Medium-entropy alloys (MEAs) offer tunable properties for advanced applications.
• Understanding the microstructural evolution and mechanical behavior of TiVNb alloys is crucial.
• Grain coarsening and dislocation dynamics significantly influence alloy performance.

Purpose of the Study:

• To investigate the effects of annealing on the microstructure and mechanical properties of a TiVNb medium-entropy alloy.
• To evaluate the high-temperature mechanical performance of the annealed alloy.
• To determine the temperature dependence of the alloy's strength.

Main Methods:

• Preparation of TiVNb alloy via vacuum arc melting.
• Annealing treatment at 1300°C for 12 hours.
• Microstructural characterization (phase analysis, grain size, dislocations, nanobands).
• Mechanical testing (hardness, tensile, and compressive strength) at room temperature and elevated temperatures (up to 800°C).

Main Results:

• Annealing at 1300°C resulted in a body-centered cubic (BCC)-dominant phase with significant grain coarsening.
• The annealed alloy exhibited Ti-rich nanobands and increased dislocation density.
• Hardness increased from 241.7 to 341.1 HV; tensile strength reached 647 MPa at room temperature and 405 MPa at 800°C.
• Compressive yield strength was 438 MPa at 800°C with reduced cracking.
• Rapid softening occurred at 1200°C, with yield strength dropping to ~50 MPa.

Conclusions:

• Annealing enhances the hardness and strength of TiVNb MEAs through microstructural modifications like nanoband formation and dislocation increase.
• The coarsened TiVNb alloy demonstrates robust mechanical strength at 800°C, with limited cracking.
• The alloy exhibits a weak dependence of strength on temperature up to 800°C, but undergoes significant softening at higher temperatures (1200°C).