Microstructural evolution and interface tensile properties of diffusion-bonded Ti55531 composite

SiC f /Ti55531 composites are critical for aerospace, yet the mechanical role of internal titanium alloy diffusion-bonded interfaces remains unclear. This study investigates the microstructure and tensile behavior of matrix/matrix and matrix/capsule interfaces fabricated via physical vapor deposition (PVD) and hot isostatic pressing (HIP). After HIP at 820 °C, a β-phase-dominated transition zone (7.7–12.9 μm) forms at the matrix/capsule interface due to elemental diffusion and PVD-induced phase transformation. While the matrix/matrix interface achieves high chemical and crystallographic continuity, the matrix/capsule interface exhibits significant crystallographic incompatibility. Tensile tests reveal an average strength of 1210 MPa (88% of the forged alloy), with fracture preferentially initiating on the matrix side of the matrix/capsule interface. TEM and EBSD analysis confirm that this failure is driven by local strain concentration and dense misfit dislocation accumulation resulting from lattice mismatch. These findings indicate that interfacial microstructural compatibility, rather than mere bonding integrity, governs the performance of SiC f /Ti composites, offering a basis for optimizing multi-interface architectural design.