Thermopower of dilute aluminium alloys and α-brass at elevated temperatures

Abstract

The thermopower of pure aluminium and of dilute alloys in the Al—Mg and Al—Mg—Si systems has been measured from 300 to 840 K using Cu and Pt as alternative standards. Measurements of thermopower over the same temperature range of two α-phase copper brasses with nominal Cu/Zn weight compositions of 70/30 and 63/37 are also reported. The data for pure aluminium have been analysed in terms of the absolute thermopower scale recently proposed by Roberts (1981) to examine the question of the separation of diffusion and phonon-drag components. In the present work a significantly smaller phonon-drag component is found than is suggested in the study by Gripshover et al. (1967). Measurements on the aluminium alloy systems emphasize the effect of metallurgical condition; for these alloys the thermopower is extremely sensitive to the presence of constituent elements in solid solution. The thermopower of α-brass in the annealed state is considerably different from that in the cold-worked condition, and its dependence on temperature is found to follow closely that of pure copper.