| With the rapid development of electric power industry, the proportion of cast aluminum alloy used in high-voltage power transmission is growing. Currently, there is no specific brand of conductive aluminum alloy, only the commonly used class of ZL101A alloy or other Al-Si alloy as a substitute, but such alloys have low electrical conductivity and their energy is easy to wear and tear, they are not reach the power industry requirements. The main purpose of this paper is to develop a new type of conductive aluminum alloy, to make the alloy meeting the mechanical properties simultaneously improving the electrical conductivity.First, effect trends of Si, Zr, Cr on electrical conductivity and mechanical properties of Al-Si alloys were analyzed by orthogonal test, the content was optimized and verified. According to reference of heat treatment and this experiment, heat treatment was determined by single test. Then according to effects of Zr and Cr on the microstructure and properties of alloys, the best content was further determined. Finally, according to preliminary studies and modification principles, modification behavior of Sb on the alloy was investigated. Effects of elements, heat treatment and modification on electrical conductivity, mechanical properties and microstructure of the alloys were investigated by electrical conductivity test, mechanical test, microstructure observation, SEM observation, EDS and XRD test, etc. These mechanisms were also analyzed.The results showed that: When alloy in cast state, electrical conductivity and tensile strength were affected most significantly respectively by Cr; Elongation was affected most significantly respectively by Zr; Hardness was affected most significantly respectively by Si; When alloy in T6 state, electrical conductivity and tensile strength were affected most significantly respectively by Si; Elongation and hardness were affected most significantly respectively by Zr. The optimal chemical composition is A13Si1Cu0.5Mg0.15Zr0.15Cr in cast state and A15SilCu0.5Mg0.35Zr 0.35Cr in T6 state. T6 heat treatment process was identified as 525±5癈×6h→180℃×10h. Electrical conductivity and mechanical properties were improved greatly after T6 treatment, beyond ZL101A alloy under the same treatment. In cast state, Al4.0Si1.0Cu0.5Mg0.35Zr0.25Cr alloy's electrical conductivityσwas 18MS/m, tensile strengthσb 183MPa, hardness HBS 66.47. However, they wereσ25.8MS/m,σb 335MPa, HBS 116 after T6 and increased respectively by 83%,53%,9% than the cast alloys. Sequence test showed:Electrical conductivity and mechanical properties of alloy were best when Zr content was 0.3% -0.35% or Cr content 0.15%. Conductivity increasing was due to that the solid solution was become uniform and orderly and reduction of lattice distortion and electronic wave scattering; As the dispersion strengthening phase precipitated and impeded dislocation movement, the mechanical properties were improved greatly. After modification by adding Sb0.2%, in T6 state, alloy's conductivity was fair or slightly lower than before modification; Tensile strength increased by 21.8%; Elongation increased by 52%; Hardness decreased. Electrical conductivity and mechanical properties of alloys in this state had been produced to meet the actual needs.Analysis showed:Adding Zr and Cr in alloy, there were many phases with Zr and Cr formed. The phases with Zr played the role of dispersion strengthening and strain hardening, and had little effect on electrical conductivity. The phases with Cr played the role of solid solution strengthening and age strengthening. Adding Sb in alloy, Sb was adsorbed on the surface of Si, which impeded the growth of eutectic Si and limited the thickness of eutectic Si. As the heterogeneous nucleation ofα-Al and eutectic Si, AlSb particle made them growing collaboratively. |
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