Investigation On Aging Treatment Of6101Aluminium Alloy

Comparing with aluminium alloy, aluminum alloy conductors have higher strength, and the comprehensive performance can be adjusted through modifying the components, processing methods and the way of heat-treatment. In this thesis,6101aluminium alloy is used to investigate the effect of precipitates on conductivity in different aging treatments, in the case of modifying homogenization heat treatment of the alloy ingots and the solid solution heat treatment of alloy rods. Some conclusions are as follows:(1) Homogenization heat treatment560℃/8h is applied to eliminate the dendrite segregation in the ingots and to dissolve the non-equilibrium eutectic phase Mg2Si into the matrix. Rod-like β-AlFeSi phase has transformed into a-AlFeSi phases, and herringbone-like and long trips-like a-AlFeSi phase are divided into many segments, which favors the plastic deformation. A solution heat treatment of525℃/1h+water-quenching is used, in which the solid solubility increases with temperature. Altough the range of520℃～530℃is appropriate for solid-solution, but leads to coarse recrystallized grains.(2) Natural aging and preaging changes the precipitation behavior of6101alumunium alloy. After water-quenching, the spontaneous natural aging produces a large number of clusters and few GP(I) zones, which can exist stably at room temperature but cannot transform into β" phase directly in the following aging treatment. After preaging at195℃/30min, the formed clusters and GP zones can be directly transformed into β" phase in the subsequent aging. The clusters and GP zones formed in natural aging and preaging increase the strain energy to strengthen the alloy but enhance the scattering of electrons,thus higher the resistivity.(3) The main strengthening precipitates are β" phase when the alloy is aged at175℃. And when at185℃and195℃the mix of β" phases and β’phases, which increases in size quickly with temperature, leads to higher strength at175℃than at185℃and195℃, but lower conductivity. The precipitates in two-stage aging treatment195℃/30min+175℃/540min are also β" phase. The precipitates size in T6temperature(175℃/720min) is21±15nm, in T7(195℃/210min) is above100nm, and in two-stage aging is10±2.5nm.(4) The effect order of the precipitates on conductivity is clusters<GP zones<β" phase<β’phase. The precipitates after aging at175℃and in two-stage aging are β" phases, of which the mean diameter grows as a function of time approximately fitted, d=3.1228-2.4689exp(-1.9501·10-4·t). The maximum mean diameter of the β" phases is approximate3.1nm, the minimum mean spacing of the β" phases is14.3nm, which dereases conductivity by10%. However, the mean size after two-stage aging is smaller, and it has larger influence on the resistivity. The kinectic formula of the resistivity of6101aluminium can be expressed as: where ρSQ、fpmax are materials constant, which can be calculated or mearured from the material, and k=1.734×10-6s-1/n, n=1.3405, calculated from the data in this thesis. The properties of T7state are, σ0.2=194.7±3.6MPa, σb=214±5.7MPa,8=14.1±0.5%, κ=59.3±0.5%IACS.