The formation of residual pores in a W-Ni-Fe alloy have been investigated. In order to confirm that these were due to the solidification shrinkage of the liquid matrix, the bar specimen of 90.8W-6.45Ni-2.75Fe with length of 40 mm was slowly cooled by pulling it along the tube at 10℃/$\min$ after being sintered at 1460℃ for 8hr in $H_2$, so that the temperature gradient might be set up along the bar specimen. A number of shrinkage pores were observed in the rear parts of the bar specimen in which liquid matrix solidified later than front parts but the front parts solidified earlier were nearly fully densified. The gas-filled pores instead of shrinkage pores formed during initial stage of liquid phase sintering were observed in the specimen dipped into the liquid of the same composition with the matrix. The sintering of the powder mixture with artificially added oxides resulted in no difference in microstructure with the other specimen. Diffusing out hydrogen from the specimen by resintering the bar specimen for 20 min in Ar gave the same result with the bar specimen with no such treatment. These results excluded the possibility that the gas formation due to oxides or difference in hydrogen solubility between the liquid and the solid might be responsible for the formation of residual pores. It was concluded that the solidification shrinkage of the liquid matrix is the direct cause of the residual pores.
