Influence of Bonding Temperature on Interfacial Microstructure and Properties of Hypereutectic Al-Si Joints with Cu Interlayer

Hypereutectic Al-27Si and Al-50Si alloys have been bonded and the influence of the bonding temperature on the microstructure and properties of the joints investigated. The results showed that Al-27Si/Al-50Si joints were bonded metallurgically with wide soldering seams containing α-Al, β-Si, and θ-Al₂Cu eutectic phases. The amount of θ-Al₂Cu eutectic phase gradually decreased and the bonding interface became nonplanar with increasing temperature. Many cracks formed in the Si phases on the Al-50Si side because of the shrinkage mismatch between the Al and Si phases and the different coefficients of thermal expansion of the Al-27Si and Al-50Si alloys. Some Si phases on the Al-27Si side transformed from granular to needle-like shape at higher temperatures. The shear strength of the joints first increased then decreased with increasing temperature, reaching a maximum of 82.3 MPa at 540°C.