Microstructural Evolutions and Mechanical Properties of Energetic Al₁ (TiZrNbTaMoCr)₁₅ High-Entropy Alloys

The present study focuses on investigating the microstructural evolutions and mechanical properties of energetic Al₁(TiZrNbTaMoCr)₁₅ refractory high-entropy alloys with the different heat treatments at low Al content state. It is found that even with a reduction in the Al content, the strength of these alloys remains unaffected at room temperature and high temperature, while the plasticity improves significantly. In particular, the coherent BCC/B2 microstructure with needle-like B2 nanoprecipitates dispersed into the BCC matrix is formed in 873 K-aged Al₁Ti₆Zr₂Nb₃Ta₃Mo_0.5Cr_0.5 alloy. Therefore, this alloy exhibits the highest compression yield strength (σ_YS = 1333 and 717 MPa) at room temperature and 1073 K, respectively. After 973 K-aged, the coherent BCC/B2 microstructure underwent destabilization, and the B2 phase transforms into the brittle Zr₅Al₃ phase which then coarsens and dominates the microstructure of S3-AlTa₃ alloy after 1073 K-aged. Moreover, these current alloys exhibit exceptionally high theoretical exothermic enthalpy (ΔH), surpassing 11606 J·g⁻¹, which highlights their significant potential as innovative high-performance energetic structural materials.