MICROGRAVITY LIQUID PHASE SINTERING AND PORE EVOLUTION

Abstract

The effect of microgravity on liquid phase sintering (LPS) in the Fe-Cu system was investigated through experiments on four sounding rockets and on three Space Shuttle missions. Three compositions, namely, Fe-33 wt.%Cu, Fe-43 wt.%Cu and Fe-53 wt.%Cu were processed for times ranging from 2.5 minutes to 66 minutes. The samples did not exhibit slumping or shape distortion during processing. However, extensive pore formation and metamorphosis was observed in all these samples. Microstructural characteristics such as densification, dihedral angle, contacts per grain, grain growth and pore metamorphosis were evaluated. The evolution of LPS microstructure in microgravity is explained using energy considerations because the liquid, solid and gaseous phases in the Fe-Cu samples seek to attain the minimum energy configuration in the absence 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 effect of composition and processing time on microstructural development in the Fe-Cu samples that have been liquid phase sintered under microgravity.