MICROGRAVITY LIQUID-PHASE SINTERING AND PORE EVOLUTION

The effect of microgravity on liquid phase sintering (LPS) in the Fe-C u system was investigated through experiments on four sounding rockets and on three Space Shuttle missions. Three compositions, namely, Fe-3 3 wt.%Cu, Fe-43 wt.%Cu and Fe-53 wt.%Cu were processed for times rangi ng from 2.5 minutes to 66 minutes. The samples did not exhibit slumpin g or shape distortion during processing. However, extensive pore forma tion and metamorphosis was observed in all these samples, Microstructu ral characteristics such as densification, dihedral angle, contacts pe r grain, grain growth and pore metamorphosis were evaluated. The evolu tion of LPS microstructure in microgravity is explained using energy c onsiderations because the liquid, solid and gaseous phases in the Fe-C u samples seek to attain the minimum energy configuration in the absen ce of gravitational forces. Therefore, the volume fractions of liquid solid and gaseous phases and processing times significantly influence the LPS microstructure in microgravity. This paper documents the effec t of composition and processing time on microstructural development in the Fe-Cu samples that have been liquid phase sintered under microgra vity.