Thermo‐Mechanical Modeling for Enhanced Thermal Shock Resistance in Alumina‒Spinel Castables

Addressing the critical challenge of thermo‐mechanical failure in alumina‒spinel castables under cyclic thermal shock, this study proposes a design strategy centered on engineered spinel‒calcium aluminate aggregates with controlled phase‑transition capability. However, the intrinsic relationship between phase‑transition content, thermodynamic response, and mechanical behavior remains insufficiently understood. Guided by CALPHAD‐based phase diagrams, aggregates with systematically graded liquid‐phase content were designed and fabricated. Their thermo‑mechanical behavior was simulated using a heterogeneous model implemented in FLAC3D, where the built‑in FISH program language was employed to reconstruct a three‑dimensional microstructure that accurately captures the random distribution of multiphase components (e.g., CA 2 , CA 6 , and CA). The model incorporates a strain‑softening/hardening Mohr‒Coulomb constitutive law to account for the effects of phase transition, including latent heat storage, viscous relaxation, and stress redistribution. Simulation results show good agreement with experimental data (error <5%). The findings reveal a systematic reduction in residual thermal stress after quenching with increasing content of low‑melting‑point calcium aluminate phases. The sample with the highest liquid‑phase content exhibits the optimal resistance to cyclic thermal shock, as the in situ generated liquid simultaneously alleviates thermal stress through latent heat absorption and viscous damping, thereby suppressing crack initiation and promoting homogeneous stress redistribution during thermal cycling. These coupled mechanisms significantly improve both the thermo‐mechanical resilience and the energy efficiency of alumina‒spinel castables under extreme operating conditions.