High-strength and energetic Al2Ti6Zr2Nb3Ta3 high entropy alloy containing a cuboidal BCC/B2 coherent microstructure

The present work developed a novel high-strength and energetic Al2Ti6Zr2Nb3Ta3 high entropy alloy (HEA) containing a BCC/B2 coherent microstructure. The microstructural evolution of BCC/B2 with both the aging temperature (873 ∼ 1073 K) and aging time (up to 200 h) was investigated, from which it was found that the cuboidal BCC nanoparticles are coherently-precipitated into the B2 matrix in 873 K-aged state due to a moderate lattice misfit (ε ∼ - 0.76%). The increase of aging temperature could destroy the BCC/B2 coherency and accelerate the formation of brittle Zr5Al3 phase. Especially, the BCC/B2 microstructure exhibits an excellent thermal stability, as evidenced by the fact that these cuboidal BCC nanoprecipitates were not coarsened obviously at 873 K with the particle size from r ∼ 10 nm in 24 h-aged state to r ∼ 20 nm in 200 h-aged state. This alloy possesses prominent mechanical properties with high yield strength at both room temperature (σYS = 1193 MPa) and elevated temperatures (1060 MPa at 873 K and 106 MPa at 1273 K), where the high strength was discussed in light of the precipitation strengthening mechanism. Importantly, the current alloy has an ultrahigh combustion calorific capacity with a value of 10240 J·g−1, showing a great potential to be used as novel high-performance energetic structural materials.