Effects of Ferroelastic LaAlO 3 on the Thermal Shock Behavior of Y 2 O 3 /LaAlO
Yilin Jia, Zhoufu Wang, Hao Liu, Yan Ma, Yunjie Dong, Haokai Song, Huimin Yu, Siyuan WuABSTRACT
In aerospace, metallurgy, and related fields, Y 2 O 3 ceramics have broad application prospects owing to their excellent high‐temperature chemical stability; however, their widespread application is limited by poor thermal shock resistance. In this study, LaAlO 3 , a toughening phase with good chemical compatibility and excellent mechanical and thermal properties, was introduced into Y 2 O 3 ceramics via an in‐situ reaction method to improve their thermal shock resistance. The property and structural evolution of Y 2 O 3 /LaAlO 3 multiphase ceramics under cyclic thermal shock and different thermal shock temperature differences were systematically investigated. The results show that the residual strength of the ceramics exhibited an exponential decreasing trend. After nine thermal shock cycles, the elastic modulus and fracture toughness of the Y 2 O 3 /LaAlO 3 multiphase ceramics were 144.6% and 121.5% of those of the Y 2 O 3 ceramics, respectively. LaAlO 3 hindered crack propagation through a pinning effect, while its ferroelastic domain‐switching mechanism effectively dissipated stress at the crack tip. The crack‐particle interaction model indicated that thermal shock cracking in the multiphase ceramics had a saturation limit. After nine cycles, the crack damage area per interaction reached approximately 90% of the damage tolerance, and the crack propagation rate continued to decrease. With increasing thermal shock temperature difference, the residual strength of the composite ceramics exhibited a nonmonotonic trend, with a residual strength retention of 73.1% after three thermal shock cycles from 800°C to room temperature. This can be attributed to the dissipation of strain energy by ferroelastic domain rearrangement and domain‐wall motion during the LaAlO 3 phase transformation. In addition, the elastic softening associated with the phase transformation improved the strain compliance of LaAlO 3 , reduced local thermal stress, and mitigated damage in the ceramics.