Residual Porosity in Tungsten Alloy

Ductility of tungsten alloy is very sensitive to residual porosity. For tungsten alloy whose tungsten content is 94%~97%, when porosity in alloy is only 1%~1.5%, tungsten alloy will be tendered completely. There are 4 reasons for causing pore containing excessive burning, rapid cooling and solidification, volatile elements existing in tungsten alloy and uneven sintering.

When tungsten pellet being spheroidized completely, connectivity of tungsten pellet is the lowest and elongation of tungsten alloy reaches maximum with that. Then pore will grow with the increasing time of sintering. Tungsten alloy will tender. When liquid sintering is finished, hydrogrn spreads rapidly in solidifying liquid phase and it causes shrinking pore when liquid phase is solidified. For that liquid phase should cool slowly. When cooling rate is higher than 10℃/min, tungsten alloy will cause more pore pores and ductility of tungsten alloy will descend. For sample whose size is large, when cooling rate is low, tungsten alloy will cause pore because of gaseous diffusion and solidifying contraction.


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