Measurement and Prediction of the Thermal and Electrical Conductivity of Al-Zr Overhead Line Conductors at Elevated Temperatures

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.

A solution to the hot cracking problem for aluminium alloys manufactured by laser beam melting

“…Indeed, the homogeneous nucleation rate is proportional to exp (− ∆ * ) where ΔG* represents the nucleation barrier at a given undercooling [35]. Taking reasonable values for the enthalpy of fusion of Al3Zr, ΔH=305J/g [36], and the solid liquid interface 28 σSL = 1 Jm -2 , the nucleation barrier at 950 K (i.e. close to the growth temperature of the αAl phase) is roughly ΔG*=1.9x10 -16 J. Normalizing by kT, ΔG*/kT is of circa 10 4 .…”

Tailoring Thermal Transport Properties by Inducing Surface Oxidation Reactions in Bulk Metal Composites

“…Figure shows data for thermal conductivities of various Al and Zr species indicated in Figures and − relative to the measured value from Figure (labeled AlZr LFA ) and a weighted average for the stoichiometric mixture of pure Al and Zr (labeled AlZr avg ). Intermetallic species such as ZrAl 3 would increase the thermal conductivity relative to the measured value.…”

“…Figure shows data for thermal conductivities of various Al and Zr species indicated in Figures and − relative to the measured value from Figure (labeled AlZr LFA ) and a weighted average for the stoichiometric mixture of pure Al and Zr (labeled AlZr avg ). Intermetallic species such as ZrAl 3 would increase the thermal conductivity relative to the measured value. Species with a higher atomic concentration of Zr may decrease thermal conductivity relative to Al rich species and internally may contribute to a lower thermal conductivity, although Figure shows no sign of Zr-rich intermetallic species at 600 °C.…”

The effect of temperature on the electrical and thermal conductivity of graphene‐based polymer composite films

“…The lower conductivity is due to electron scattering resulting in a sharp decrease in the mean free path of electrons. 41 Graphene flakes were aligned in a plane creating conductive channels where electrons were able to pass across the polymer matrix that has a very low conductivity value. 32 The energy of carbon atoms is at a low level when the temperature is low; however, they acquire more energy and start to vibrate across their mean positions when the temperature increases.…”