MEASUREMENT OF THE HEAT OF FUSION OF TUNGSTEN BY A MICROSECOND-RESOLUTION TRANSIENT TECHNIQUE

A microsecond-resolution pulse-heating technique was used for the meas urement of the heat of fusion of tungsten. The method is based on rapi d (100 to 125 mus) resistive self-heating of a specimen by a high-curr ent pulse from a capacitor discharge system and measuring current thro ugh the specimen and voltage across the specimen as functions of time. Melting of a specimen is manifested by changes in the slope of the el ectrical resistance versus time function. The time integral of the pow er absorbed by a specimen during melting yields the heat of fusion. Me asurements gave a value of 48.7 kJ.mol-1 for the heat of fusion of tun gsten with an estimated maximum uncertainty of +/-6 %. The electrical resistivity of solid and liquid tungsten at its melting temperature wa s also measured.