Microstructural Characteristics and Vibration Fracture Properties of Al-Mg-Si Alloys with Excess Cu and Ni

Abstract

This study investigated the effect of co-addition of Cu and Ni on the microstructure and vibration properties of Al-Mg-Si alloys. The results show that additions of Cu and Ni resulted in the formation of Al3(Ni,Cu) phase, a harder Al matrix and an accelerated aging rate. Nanoindentation analysis indicates that the Al3(Ni,Cu) phase exhibits a hardness of 7.7 GPa and Young’s modulus of 141.2 GPa. Due to the increased modulus by reinforcement effect of Al3(Ni,Cu), the alloyed samples possessed a higher resonant frequency. However, the damping capacity was reduced with alloying because of the hardened matrix. It was also found that since microcracks could be generated from the irregular-shaped Al3(Ni,Cu) in the vicinity of the tip of the main crack when suffering vibration deformation, the crack propagation resistance of the alloyed samples was inferior.