Suk-Joong L. Kang

KAIST, Department of Materials Science end Engineering, Daejeon 34141, Republic of Korea

Densification of a powder compact, the primary goal of sintering, is affected by various processing parameters, including the particle/pore size and distribution, and the thermal cycle (sintering temperature and heating rate). The effects of these parameters have been closely and widely analyzed for systems without grain growth in most cases. Sintering theories so developed can predict the densification kinetics with respect to certain processing parameters, in particular the particle size and sintering temperature. For full densification of the powder compact, however, it is essential to prevent the entrapment of isolated pores within growing grains and to retain them at the grain boundaries. Theories of microstructural evolution in porous systems have been developed in terms of the relative kinetics of densification and normal grain growth. To achieve full densification, grain growth, abnormal grain growth (AGG) in particular, must be suppressed. When AGG takes place, many isolated pores can be entrapped within growing grains, a process which limits the densification.

This presentation will discuss general directions for the full densification of powder compacts. First, we will briefly review the effects of the particle size and powder packing on densification. The effect of the thermal cycle will also be reviewed. Based on the recently established mixed mechanism principle of microstructural evolution, strategies for suppressing AGG will be presented.