Vacuum brazing of dissimilar aluminium alloys

• Main Author: Wong, Chun Long
• Other Authors: Zhou Wei
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/167996
• Institution: Nanyang Technological University

There are many engineering applications for joining dissimilar aluminium alloys. For example, electronic packaging and valve lining in engines. This report investigated the effects of brazing temperature on the strength of the brazing joint in the context of vacuum brazing for dissimilar aluminium alloys. In this study, high-strength 7xxx Al and high-Si Al alloys were brazed in the vacuum furnace. The brazing filler was a copper foil, and the brazing experiments were performed in a vacuum furnace. The shear strength of the brazing joint first increased as the brazing temperature increased before it slightly dropped at the highest brazing temperature. The increase in shear strength was due to the occurrence of the Q phase, which has not been previously reported in the literature, highlighting a novel finding in our study compared to similar investigations. Further analysis revealed alloy composition's critical role in forming the Q phase. A denser Q phase increased the strength of the brazing joint. However, at the highest brazing temperature, the strength of the brazing joint decreased due to the effects of residual stress caused by the difference in coefficient of thermal expansion between the Al alloys.