Development of Low-Density AlNbTaTiZr Refractory High-Entropy-Intermetallic-Alloy: Microstructural Evolution, Mechanical Properties, and High-Temperature Deformation

This study investigates the structural evolution, mechanical properties and high-temperature performance of a novel low-density refractory high entropy intermetallic alloy (RHEIA); Al₁₂Nb_25.5Ta_8.5Ti_27.5Zr_26.5. The alloy was prepared by vacuum arc melting, homogenized and subjected to various heat treatments at 600°C, 800°C and 1000°C. The resulting microstructure was revealed using scanning electron microscopy (SEM) with attached electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), X-ray diffraction (XRD). The as-received RHEIA showed an initial yield strength of ~1398 MPa, a specific yield strength of 202 MPag⁻¹cm³ and ductility >50%. Heat treatment at 600°C, enhanced the yield strength to 1828 MPa, though ductility reduced to 20%; attributed to formation of Al-Zr-rich nanoprecipitates in B2 matrix. Whereas, the decrease in yield strength with some improvement in ductility was observed, after heat treatments at 800°C and 1000°C, driven by the reduced entropy effects and coarsening of the binary intermetallic. Further, the RHEIA demonstrated a stable high temperature deformation behaviour up to 600°C exhibiting yield strength of 1026 MPa, whereas the strength reduces to 450 MPa and 70 MPa at 800°C and 1000 ⁰C, respectively. The findings highlight Al₁₂Nb_25.5Ta_8.5Ti_27.5Zr_26.5 RHEIA’s potential for applications requiring balanced strength and weight under extreme conditions and advances phase transformations knowledge of RHEIAs.