Enhanced high‐temperature strength in textured (Ti1/3Zr1/3Hf1/3)B2 medium‐entropy ceramics via strong magnetic field

Abstract

AbstractThis study prepared textured (Ti1/3Zr1/3Hf1/3)B2 medium‐entropy ceramics for the first time that maintain enhanced flexural strength up to 1800°C using single‐phase (Ti1/3Zr1/3Hf1/3)B2 powders, slip casting under a strong magnetic field, and hot‐pressed sintering methods. Effects of WC additive and strong magnetic field direction on the phase compositions, orientation degree, microstructure evolution, and high‐temperature flexural strength of (Ti1/3Zr1/3Hf1/3)B2 were investigated. (Ti1/3Zr1/3Hf1/3)B2 grain grows along the a,b‐axes, resulting in a platelet‐like morphology. Pressure parallel and perpendicular to the magnetic field direction can promote the orientation degree and hinder the texture structure formation, respectively. Reaction products of W(B,C) and (Ti,Zr,Hf)C between (Ti1/3Zr1/3Hf1/3)B2 and WC additive can efficiently refine the (Ti1/3Zr1/3Hf1/3)B2 grain size and promote grain orientation. (Ti1/3Zr1/3Hf1/3)B2 ceramics doped with 5 vol.% WC yielded a Lotgering orientation factor of 0.74 through slip casting under a strong magnetic field (12 T) and hot‐pressed sintering at 1900°C. Furthermore, cleaning the boundary by W(B,C) and introducing texture can enhance the grain‐boundary strength and improve its high‐temperature flexural strength. The four‐point flexural strength of textured (Ti1/3Zr1/3Hf1/3)B2‐5 vol.% WC ceramics was 770 ± 59 MPa at 1600°C and 638 ± 117 MPa at 1800°C.