Theory of liquid-phase sintering: model experiments on W-Ni-Fe heavy alloy system
Current liquid-phase sintering theories predict negligible densification prior to the formation of a liquid phase. While these theories are fully applicable to a few model systems, their validity is questionable under more general circumstances. Experiments on a 93% W-Ni-Fe heavy alloy show that nearly 94% of the total shrinkage occurs prior to liquid formation. In this study, densification behavior has been studied by means of constant heating rate dilatometry. The microstructural evolution during sintering was monitored by quantitative microscopic examination of samples quenched from various temperatures during heating. The actual amount of densification that occurs prior to liquid formation is observed to be a function of both material process parameters. It was found that the contribution of solid-state-enhanced sintering to densification increases with slower heating rates. Thus, the role of rearrangement in densification during liquid-phase sintering is of less importance in common commercial systems (like W-Ni-Fe), where the additive phase exhibits solubility for the major phase. Rearrangement becomes important only at faster heating rates, especially in low solubility systems. This paper demonstrates that the mechanisms proposed by current theories are inadequate to explain densification behavior during liquid-phase sintering. Finally, an alternative approach to understanding liquid-phase sintering is suggested; and the new theory is outlined.
- Research Organization:
- Rensselaer Polytechnic Inst., Troy, NY (USA). Dept. of Materials Engineering
- OSTI ID:
- 5002852
- Report Number(s):
- AD-A-190537/1/XAB
- Resource Relation:
- Other Information: Pub. in Progress in Powder Metallurgy, Vol. 43, 65-77(1987)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Theoretical concepts for the liquid phase sintering of a new low temperature tungsten heavy alloy. Ph.D. Thesis
Phase equilibria effects on the enhanced liquid phase sintering of tungsten-copper
Related Subjects
IRON ALLOYS
SINTERING
NICKEL ALLOYS
TUNGSTEN BASE ALLOYS
COPPER
DENSITY
GRAIN GROWTH
LIQUIDS
MICROSTRUCTURE
SOLUBILITY
ALLOYS
CRYSTAL STRUCTURE
ELEMENTS
FABRICATION
FLUIDS
METALS
PHYSICAL PROPERTIES
TRANSITION ELEMENTS
TUNGSTEN ALLOYS
360101* - Metals & Alloys- Preparation & Fabrication