The specific surface area of the powder surface will change because of the size of the powder particles, when the powder particles are large, the specific surface area will decrease, when the powder particles are small, the specific surface area will increase, the size of the specific surface area relates to the size of the surface energy provided by the powder during sintering, a large specific surface area with a large surface energy can be completed at lower temperatures or externally provided by the smaller energy to complete the sintering, on the contrary, a small specific surface area is On the contrary, a small specific surface area has to rely on a larger external energy to complete the sintering action. In the process of sintering, the high temperature will cause the movement of atoms, the distance between the powder and the two particles of the powder to change, resulting in the reduction of surface area, shape changes, to the density of the rise, and then complete the sintering action. Generally speaking, conventional sintering can be organized into the following six diffusion mechanisms, all of which are diffused in different ways to the concave neck position between two powder particles, as follows:
The convexity of the atomic particles spreads out through the surface path to the neck, which becomes thicker but not denser. This mechanism is more pronounced than others at low temperatures or when sintering has just begun.
- Evaporation and Condensation：
Atomically convex surfaces evaporate and condense at the neck, and this mechanism does not result in densification. In the sintering process, this mechanism applies to substances with higher vapor pressure, while substances with lower vapor pressure tend to follow the diffusion path of other solid phases.
Atoms diffuse from the grain boundaries between particles to the neck, which is the mechanism of densification.
Atoms in the vicinity of intergranular grain boundaries move to the neck via bulk diffusion, and the principle of densification is the same as that of grain boundary diffusion.
- Volume Diffusion Atom From Surface：
Atoms on the convex surface of the particles move to the neck by body diffusion, a process that does not result in densification.
- Volume Diffusion Atom From Dislocation：
Atoms move from the differential rows inside the particle to the neck, which is the mechanism of densification.
