Fully dense Nb/Nb5Si3 in-situ composites were successfully prepared by SPS smelting-casting

and phase constituent and microstructure of the composites were investigated by XRD （X-ray diffraction）

SEM （scanning electron microscope）

EPMA （electron probe micro-area analysis） and EDS（energy disperse spectroscopy）. The results indicate that microstructure of the Nb/Nb5Si3 in-situ composites prepared by SPS smelting-casting is composed of near-spherical primary Nb particle and （Nb+Nb5Si3） eutectoid

and with increasing in cooling rate

near-spherical primary Nb particle and （Nb+Nb5Si3） eutectoid are refined gradually. Prepared composites reach 99.69% theoretical density in density. Integration of in-situ synthesis with liquid forming can be realized in preparation of Nb/Nb5Si3 in-situ composites by SPS smelting-casting.