In recent years, the severe energy consumption identified in the global powertransmission process makes the development of new generation of transmission materials with high strength (mainly the ultimate tensile strength) and outstanding electrical conductivity (EC) more urgent. Though Al and its alloys received significant attention from the scientific community in the past two decades due to their relatively high mechanical properties and excellent EC, increasing strength and EC are often incompatible in Al conductor alloys, which remains unresolved. Therefore, the ways to achieve the optimal compromise between the strength and EC has become a hot topic in current researches. This review focuses on the high-strength conductive Al alloys that have been studied by researchers in the past two decades, and endeavors to reveal the relationship between the EC and the strength based on composition, microstructure, interface, and others. Moreover, the design ideas and treatment measures considering both conductivity and strength are also summarized.
With the increasing demand requirements of lightweight automobiles, foundry industries are facing urgent requests from the demanders to manufacture increasingly lighter castings with thin walls and complex shapes. Fluidity is the essential parameter to evaluate the filling ability of casting alloys. Many factors are affecting the fluidity of casting Al–Si series alloys. In this review, the current understanding of the various factors influencing the fluidity of casting Al–Si series alloys was systematically summarised. Moreover, the solidification mechanism of hypoeutectic Al–Si alloys under the high-pressure die casting (HPDC) process is also discussed. HPDC process is not inversely proportional to the solidification interval, but the fluidity length increases with decreasing solidus temperature of the hypoeutectic Al–Si alloys.
Binary Al-Cu alloy has always been used to illustrate the phenomenon of precipitation hardening. Meanwhile, Al-Cu alloy has good heat resistance and is a potential heat-resistant conductor material, but there is not much research work on its electrical properties. In this work, the residual resistivity variation of Al-4Cu alloy at different aging stages was investigated. At the aging temperature of 160 ℃, the residual resistivity of the Al-4Cu alloy decreases with the longer aging time, and it decreases rapidly in the early stage and slowly in the later stage, mainly due to the precipitation of solid solution Cu atoms and the interface electron scattering effect of different precipitates. In the early stage, massive precipitation of Cu atoms from the matrix can effectively reduce the crystal lattice distortion of Al matrix and significantly decrease the residual resistivity. Specifically, the residual resistivity of Al-4Cu alloy that aged at 160℃ for 13h is 3.353 μΩ·cm, which is only 82.6% of that in the supersaturated solid solution state. In later stage of aging, the main change is the evolution of the precipitated phase, i.e., the gradual disruption of the coherent relationship between the second phase and the Al matrix. And the coherency-strain fields decrease gradually, which is also beneficial in decreasing the residual resistivity. The results show that Al-Cu alloys can also be a potential heat-resistant conductor material for the power transmission industry.
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