Determination of thermal conductivity of magnesium-alloys

Abstract

An indirect method, Angstroms method was adopted and an instrument was designed to determine the thermal conductivity of magnesium metal and alloys. Angstroms method is an axial periodic heat flow technique by which the thermal diffusivity can be measured directly. Then thermal conductivity can be obtained with relation to thermal diffusivity. Compared with the recommended data from the literature the fitted values of the thermal diffiusivity correspond with 3%, and the credible probability of the thermal conductivity in the range of 0-450 °C is about 95 %. The method is applicable in the given temperature range. Document code: AThermal conductivity and thermal diffusivity are crucial to metallic materials as they affect the heat transfer rote in the processing process and therefore, influence the thermophysieal performance of the metal products. Therefore, it is of importance for metallurgical industry to determine them precisely. In this research, magnesium metal and alloys were measured to investigate the relationship between the alloying component and the thermal conductivity, and find the dependence of thermal conductivity on temperature.1 Experimental principle and instrument 1.1Angstroms method for measuring thermal conductivity Angstroms method is an axial periodic heat flow technique Ejal . A long cylindrical specimen was rested at one end on a heater which generated periodic heat flow, and two temperatures were taken by thermocouples mounted at different height of the cylinder. The thermal diffusivity of the specimen could be calculated by measuring the decreasing amplitude or increasing phase lag between the thermocouples as the heat wave propagated through the specimens in its axial direction. The following i n [33 express o s are used in the calculation: at. = P(AX)Z/4rr(£xt) (1) a, = 7r(AX)Z/Pln2( 02/0, )where aL--thermal diffusivity due to the phase lag, m2/s; a,--thermal diffusivity due to amplitude decrement, m2/s; P--the period of the wave of axial heat flow, s; AX--axial distance between the thermocouples, m; At--the phase time lag, s; 0~, 02--amplitude at thermocouplel,2, °C.The value of the diffusivity, calculated from the expression, may differ from each other, due to radial heat transfer between the specimen and the surroundings. This can be taken into account by a correction factor, 2rr(Ax) F~ = I Pln(02/0~ ) tand F~ = 1/F~where FL, F~--the correction factors of aL, aa •

The Influence of Heat Treatment Parameters on the Thermal Diffusivity of WE54 and Elektron 21 Magnesium Alloys

“…They are crucial to metallic materials as they affect the heat transfer rate in the processing process and therefore, influence the thermophysical performance of the metal products. Therefore, it is of importance for metallurgical industry to determine them precisely [4]. In the literature, however, almost no data are available on the thermal properties of WE54 and Elektron 21 alloys.…”

Thermal properties of Mg–11Y–5Gd–2Zn–0.5Zr (wt.%) alloy

“…Fig. 6 shows the values of the thermal diffusivity of WGZ115 alloy with the literature values of pure Mg and AZ91 alloy for comparison [15,16]. At room temperature the thermal diffusivity is 14.3 × 10 −6 m 2 s −1 , while it reaches to 21.2 × 10 −6 m 2 s −1 at 300 • C. Thermal conductivity values are calculated from the following equation [17]:…”

The Thermal Diffusivity of Mg-Al-Sr and Mg-Al-Ca-Sr Sand Casting Magnesium Alloys

“…They are crucial to metallic materials as they affect the heat transfer rote in the processing process and therefore, influence the thermophysical performance of the metal products. Therefore, it is of importance for metallurgical industry to determine them precisely [7]. In the literature, however, almost no data are available on the thermal properties of the Mg-Al-Sr and Mg-Al-Ca-Sr alloys.…”