Electrical Resistivity Of Liquid Research Articles

Solidification Behavior of AZ31 Magnesium Alloys Using an Electromagnetic Vibration Technique

The commercial magnesium-based AZ31 alloy was solidified in a static magnetic field when an alternating electric current, perpendicular to the direction of the magnetic field, passes through the alloy. In this case, the periodical Lorentz force is generated, making the conductor vibrate centering on the initial equilibrium position. In this paper, we investigated the microstructure evolution of the alloy as a function of vibration frequency, magnetic flux density and electric current, respectively. The solidification behavior was discussed and the mechanism for the formation of the microstructure was proposed when considering the electrical properties of solid and liquid at high temperature. Because the electrical resistivity of liquid in the mushy zone is about twice that of the solid, this significant difference drives the solid to move faster than the liquid and thus generating a leading displacement for the solid over the liquid even within one vibration cycle. The uncoupled movement between the solid and liquid also gives rise to melt flow, which may be the reason to segment dendrites into fine particles. Meanwhile, the uncoupled movement makes it difficult to establish a steady state for solute redistribution during solidification and thus favoring equiaxed structures instead of dendrites. Considering these two factors, we examine the solidification behavior of the alloy separately when vibration frequency, magnetic flux density, and electric current are set as independent variables and the microstructure evolution as a function of these processing parameters can be well interpreted.

Thermopower and electrical resistivity of liquid and crystalline Dy and Ho at temperatures 300–2000 K

The first measurements of the thermopower, S(T), of the rare earth metals Dy and Ho in the liquid state have been completed. For each metal S (and electrical resistivity, ϱ) were measured at temperatures from 300 K up to 2000 K. The measurements above the melting temperatures ( T m = 1680 K for Dy, T m = 1734 K for Ho) were performed on samples held in Ta-containers. The influence of the sample purity, particularly involving gaseous impurities, on the high temperature transport properties was investigated. The electrical resistivity in the liquid state is only slightly temperature dependent for these metals, whereas the thermopower shows a greater temperature variation, with d S/d T being non-linear, but averaging about − 0.03 μV/K 2 for each metal The experimental data are compared with various theoretical models, and the effect of thermal smearing of the Fermi distribution function at high temperatures is discussed.

Electrical resistivity of ternary glassy and liquid Pd-alloys

The electrical resistivity of liquid (Pd 100Cu 100− x ) 80Ge 20 alloys has been measured as a function of temperature. For Cu-rich negative temperature coefficients and for Pd-rich alloys positive temperature coefficients of the electrical resistivity have been observed. This behavior is very similar to recent observed resistivity temperature curves of glassy (Pd 100Cu 100− x ) 80P 20 alloys. An explanation of the resistivity behavior in terms of liquid metals theory is suggested.

Electrical resistivity of liquid and solid sodium

The electrical resistivity of sodium contained in a stainless-steel capillary has been determined between 19 and 300° by means of a Kelvin–Wheatstone Bridge. The resistivity of the liquid between 97·8 and 300° obeys the equation ρL(µΩ cm.)=a+bT+cT2+dT3–eT4 where T is in °C, and the constants have the values: a, 6·87; b, 2·44 × 10–2; c, 2·67 × 10–5; d, 1·07 × 10–7; e, 2·67 × 10–10. The corresponding equation for the solid over the temperature range 19–97·8° is ρS(µΩ cm.)=a+bT+cT2+dT3 where the constants are: a, 4·35; b, 2·13 × 10–2; c, 6·25 × 10–6; d, 1·04 × 10–7. The results are compared with published values, and factors responsible for the variation in resistivity with change of phase are considered briefly. The design of apparatus whereby spurious post-melting phenomena are avoided is discussed.