Multiscale phase-field simulation framework for spinodal decomposition behavior in composite carbide ceramics

In traditional carbide ceramics, the inherent trade-off between hardness and toughness limits performance under extreme conditions. Spinodal decomposition enables the formation of nanoscale lamellar structures that simultaneously enhance both properties, yet precise control over microstructural evolution during aging remains challenging. This study develops a multiscale phase‐field simulation framework to clarify the formation mechanisms and mechanical contributions of lamellar structures in (Ti, Hf)C ceramics. Systematic experiments evaluated the effects of aging time and temperature on microstructure and properties. Initially, the phase‐field crystal method was applied to identify grain boundary defects, yielding critical insights. Subsequently, phase‐field simulations based on experimental data and key parameters investigated spinodal decomposition with an emphasis on its synergistic impact on crack propagation. Ultimately, (Ti_0.5, Hf_0.5)C achieved optimal performance after 10 h of aging at 1500°C, with a hardness of 2745 HV and a fracture toughness of 3.21 MPa m^1/2.