Abstract
In order to determine the solid-liquid interfacial tension and its temperature dependence of the W-Cu system, the contact and dihedral angles were measured by multiphase equilibrium experiments in the range of temperature, 1573∼1873 K.
In these experiments, the contact angle at the solid-liquid-vapour line was determined by the sessile drop method. The dihedral angle (φSL) at the grain boundary groove in contact with liquid was determined from the SEM microstructure of liquid-phase sintered materials, and the dihedral angle (φSV) at the groove in contact with vapour was determined from the groove configuration trace by a SEM height meter.
The temperature dependence of the solid-liquid interfacial tension determined (σSL) was examined together with those of the grain boundary tension (σSS) and surface tension (σSV) of solid tungsten.
The following results have been obtained:
(1) The contact angle was 5° at 1473 K. At temperatures higher than 1573 K spreading of copper took place and the contact angle was estimated to be 0°.
(2) φSL and φSV were 85.3-95.0° and 143.7-144.3°, respectively. Both values decreased with an increase in temperature.
(3) A plot of σSL against temperature shows a linear relationship as represented by the following equation:
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oindentThe experimental error of σSL was in ±5% and d(σSL)⁄dT was −0.63±0.03 mN/(m·K).
(4) The temperature dependence of σSS and σSV can be represented by the following linear relationships:
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oindentIn the above equations d(σSS)⁄dT and d(σSV)⁄dT were −0.49±0.02 and −0.91±0.03 mN/(m·K), respectively.
