Evolution of Microstructure, Mechanical Properties and Residual Stress Prediction of Al2O3 Ceramic/TC4 Alloy Diffusion Bonded Joint

This study systematically investigates the microstructure evolution, mechanical properties, and residual stress distribution in diffusion-bonded joints between Al2O3 ceramic and TC4 alloy. Motivated by the need for reliable high-temperature joints in advanced applications, this work addresses the challenges posed by the materials’ physicochemical differences. Joints were fabricated at temperatures ranging from 800 °C to 950 °C under a pressure of 3 MPa for 2 h. Microstructural characterization revealed the formation of a multi-layered interfacial structure, dominated by a Ti3Al reaction layer, whose thickness increased with bonding temperature. The highest shear strength of 54 MPa was achieved at 850 °C, representing a key quantitative outcome of this parameter optimization. Beyond this temperature, excessive growth of the brittle Ti3Al layer and associated residual stresses led to strength degradation and interfacial cracking. A three-dimensional finite element model was developed to simulate residual stress distributions, highlighting significant tensile stresses within the Ti3Al layer and compressive stresses in the Al2O3 near the interface. The model further identified critical tensile stress concentrations along the vertical edges of the ceramic, which contribute to failure during shear testing.