No abstract

In the present work, the thermal conductivity and electrical resistivity of the Al-0.25 Zr (wt.%) alloy have been investigated from 300 K to 600 K. The variations of thermal conductivity (K total) with temperature were measured by using a radial heat flow furnace. The electrical resistivity (ρ) measurements of the alloy depending on the temperature were performed using the standard four-point probe method. The electrical conductivity (σ) was obtained by using the measured electrical resistivity. The thermal conductivity and the electrical resistivity coefficients were determined from the graphs of thermal and electrical resistivity versus temperature for the alloy. The electronic thermal conductivity (K e) values were obtained from the Wiedemann-Franz and Smith-Palmer equations, and the values of K L were obtained by subtracting K e fromthe measured values (K total). K total is dominated by Ke, and K e varies between 208-198 W/mK. The K L decreases from 7.99 to 1.77 W/m K, and σ varies between 1.41x10 7-2.80x10 7 Ω-1 m-1 in the range of temperature 373-600 K. The enthalpy of fusion (ΔH) and the specific heat capacity (C p) during the transformation were determined. Thermal diffusivity (α) changes were calculated as a function of temperature from these obtained thermal data.

Different kinds of Al and Al alloys are used for all bare overhead energy transmission lines. In the present work, the effect of heat treatments on the conductivity of Al-0.25wt.%Zr alloy has been investigated. Al-0.25wt.%Zr samples were prepared in cold graphite crucibles by using a vacuum furnace and a continuous casting line. The samples were aged isothermally and isochronally in muffle and tube furnaces. Aging was carried out at a wide range of temperatures (350-600 °C) at constant aging times (75 h, 100 h) and a wide range of aging times (25-500 h) at constant temperatures (425 °C, 450 °C). According to the experimental results, conductivities of aged samples increase up to a certain aging temperature and aging time and reach peak values, then decrease with increasing aging temperature and aging time.

Aluminium and its alloys are used in all bare overhead energy transmission lines. Researchers and manufacturers, have in the past, made significant improvements in the tensile strength and conductivity of overhead lines. In the present work, the effect of heat treatments on the tensile strength of Al-Zr alloys (Al-0.15, 0.20, 0.25wt.%Zr) has been investigated (all compositions hereafter are described in wt.%). The Al-Zr samples were prepared by using a melt furnace and a continuous casting line. The cast, extruded and drawn samples with different diameters (4, 6, 10 mm) were aged isothermally and isochronally in muffle and tube furnaces. Aging was performed over a wide range of temperatures (350-450 °C) at constant aging times (100 hrs., 125 hrs.) and over a wide range of aging times (50-150 hrs.) at a constant temperature (425 °C). It was found that, aging temperatures, aging times, composition, processing techniques and size of the samples affect the tensile strength.