Phase boundary transition layer design and strengthening-toughening theory of Y2O3/LaAlO3 composite materials

Yttrium oxide materials exhibit excellent vacuum and high-temperature chemical stability as well as low wettability with alloys, making it ideal for superalloy smelting. However, its poor sinterability and low fracture toughness, which result in poor thermal shock resistance significantly limit its service life. This study focuses on yttrium oxide materials. By incorporating ferroelastic functional unit characteristics, a pre-synthesized LaAlO 3 phase with good intrinsic toughness was introduced into the Y 2 O 3 matrix. The effects of different LaAlO 3 contents on the phase composition, microstructure, mechanical properties, and thermal shock stability of the composite materials were systematically investigated. Results indicate that Y 2 O 3 /LaAlO 3 composite materials can be prepared successfully by regulating the La 3+ segregation behavior to form a transition layer at the phase boundary. This method can significantly enhance both the strength and toughness of materials through the ferroelastic domain switching effect and the solid solution effect. These mechanisms are capable of effectively improving the material's resistance to crack propagation and thermal stress relaxation, thereby improving the thermal shock resistance of the composites under thermal shock conditions. When 15 mol% LaAlO 3 was added to Y 2 O 3 , the fracture toughness of the composite material increased to 4.65 ± 0.14 MPa m 1/2 . The residual strength retention of the composite material increased from 36.50 % to 43.38 % after thermal shock. Therefore, by constructing a phase boundary transition layer through La 3+ ion solid-solution, Y 2 O 3 /LaAlO 3 composite materials can be prepared, effectively enhancing both the mechanical properties and thermal shock resistance of Y 2 O 3 matrix ceramics, offering a viable strategy for designing high-performance oxide ceramics.