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 Al 3 (Ni,Cu) phase, a harder Al matrix and an accelerated aging rate. Nanoindentation analysis indicates that the Al 3 (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 Al 3 (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 Al 3 (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.

Effect of nickel on the microstructure and mechanical property of die-cast Al–Mg–Si–Mn alloy

“…Currently, it is not clear yet for the association between α-AlFeMnSi and Ni in the experimental alloy. It was observed that Al 3 Ni were formed in a fairly low Ni content in Al-Mg-Si wrought alloys [16,18], which is not consistent with the results in this work. However, the differences between previous work and this work is obvious because the Fe content is low in the wrought alloy and the Mn content is relatively high in the alloy in this work.…”

“…% at 450 o C [17]. In the Al-Ni binary alloy, the addition of nickel up to 2 wt.% gives an increase in the strength of aluminium, but a decrease in ductility [18]. Similar results were found in multicomponent aluminium systems and the aluminium matrix is unlikely to contain Ni levels above the equilibrium solubility.…”

“…It is clearly seen that (1) the Ni-rich intermetallics essentially consisted of Fe, Mn and Si, and no Al 3 Ni phase was detected in the studied alloy with Ni content up to 2.06 wt.%; and (2) two types of Ni-rich intermetallics had the same constituent composition and could be described by the same chemical formula. It is noticeable that the Ni-rich intermetallic phase formed in the alloy was different to the intermetallic phases observed in other Al-Si-Mg alloys [18]. Song et al found that Al 3 Ni were formed in the alloys with 1.4 wt.% Ni.…”

“…Similar results were found in multicomponent aluminium systems and the aluminium matrix is unlikely to contain Ni levels above the equilibrium solubility. It was reported that Ni was mainly associated with iron in the form of AlFeSi intermetallics at low levels and in the form of Al 3 Ni intermetallics at higher concentrations, such as in an Al-Mg-Si wrought alloy containing 1.4wt.% Ni [18]. A recent investigation [16] has also shown that Ni additions up to 0.05 wt.% did not have an obvious influence on the phase constituents of AA6063 alloy.…”

“…For A356 alloy, Ni additions up to 0.02 wt.% did not a have significant influence on the as-cast microstructure, but a new phase was formed when the Ni addition was increased to 0.05wt.%. These intermetallics have been found to be AlFeMgSi and AlFeSi phases in the as-cast and heat-treated A356 alloy [18,19]. Therefore, it is important to verify whether Ni is an impurity or a useful alloying element in aluminium alloys.…”