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); Al12Nb25.5Ta8.5Ti27.5Zr26.5. The alloy was prepared by vacuum arc melting, homogenized and subjected to various heat treatments at 600 degrees C, 800 degrees C and 1000 degrees 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 similar to 1398 MPa, a specific yield strength of 202 MPag(-)(1)cm(3) and ductility > 50 %. Heat treatment at 600 degrees 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 degrees C and 1000 degrees 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 degrees C exhibiting yield strength of 1026 MPa, whereas the strength reduces to 450 MPa and 70 MPa at 800 degrees C and 1000 degrees C, respectively. The findings highlight Al12Nb25.5Ta8.5Ti27.5Zr26.5 RHEIA's potential for applications requiring balanced strength and weight under extreme conditions and advances phase transformations knowledge of RHEIAs.