Liquid-phase sintering mechanism

Key words a-silicon carbide, liquid phase, sintering, mechanical properties, microstructure... 

The manufacturing process (especially the cold and hot compaction stages) of pcBN is very similar to that of pcD, summarized in Section 1.3.3. However, the types of binders used and liquid phase sintering mechanisms can be quite different. In pcBN production, reactive sintering plays a major role in terms of driving the densification process, whereas in pcD, dissolution and precipitation and/or adhesion/coalescence are the main driving mechanisms. A typical example for pcBN would be the following reaction [162]. 

Liquid-phase sintering is significantly more complex tlian solid-state sintering in tliat tliere are more phases, interfaces, and material transport mechanisms to consider. In general, densification will occur as long as it is... 

Figure 1. Microstructure of a ceramic produced by liquid phase sintering showing rounded grains, some residual porosity, and the intergranular glassy phase resulting from the liquid phase. (From R. W. Davidge, Mechanical Behavior of Ceramics, copyright 1979, p. 14. Reprinted with the permission of Cambridge University Press.)...

Figure 2. Schematic diagram illustrating the three stages of liquid phase sintering, with the dominant mechanisms and processes for each stage. (After Ref 1.)...

This mechanism is similar to the one occurring during liquid-phase sintering, where the dissolution of crystalline material into the glassy phase occurs at the interfaces loaded in compression and their reprecipitation on interfaces loaded in tension. The rate-limiting step in this case can be either the dissolution kinetics or transport through the boundary phase, whichever is slower. This topic was discussed in some detail in Chap. 10, and will not be repeated here. 

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