Investigations on the Microstructural Evolution of SiC/Cu-ABA/Ti6Al4V Braze Joints Subjected to Thermal Cycles
摘要
Advanced aerospace components require robust joints between nonmetallic and metallic materials, such as silicon carbide (SiC) and Ti6Al4V alloy, to achieve adequate mechanical strength and thermal stability. In this study, SiC and Ti6Al4V alloy were successfully vacuum brazed at 1030 °C for 20 min using a Cu-based active brazing alloy in a ceramic IN–metal OUT joint configuration with a wide joint clearance. The interfacial microstructure of the braze joint was characterized using optical microscopy (OM), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). Mechanical properties were evaluated through Vickers microhardness and shear strength tests. High-temperature thermal cycling was conducted between room temperature and 700 °C, with a 15-minute dwell time, to assess joint integrity and crack formation. The results revealed the formation of a thin TiC reaction layer at the SiC interface and TiCu-based intermetallic compounds at the Ti6Al4V interface, confirming a strong metallurgical bond. Microcracks were primarily observed in the TiC and Ti5Si3 reaction layers after the fifth thermal cycle. By the seventh thermal cycle, crack propagation was evident within the braze layer and at joint corners. The braze joint demonstrated a shear strength of 35 MPa, highlighting its potential for aerospace applications requiring joint durability under cyclic thermal loads.