Sintering is, a heat treatment to get the physical and
mechanical properties required in powder compact by
making chemical bonding composed by 1st binding
strength between elements through heating
compressed/uncompressed powder compact under the
temperature below M.P of main metal element, which is
only maintained by weak binding strength or contact.
There are two sintering methods of liquid phase sinter
ing and solid phase sintering. Solid phase sintering is a
one to induce the binding between powder by heat treatment in temperature below m.p of powder, and liquid
phase sintering indicates when one or more components
form the liquid phase within sintering body in multi-
elements system. It is produced by liquid phase sinter
ing that the each kind of ceramic manufactures as well
ultra hard metal, hard metal, and some of densely
casting components. In this experiment, it has been
studied about solid phase sintering.

The general steps for sintering are as follows:
(1) Initial binding between particles,
(2) Growth of contact neck,
(3) Close of pore-channel,
(4) Globalization of pore,
(5) Pore contraction and termination (or densification),
(6) Pore Coarsening.
Sintering of nickel powder, the initial contact point (in A) is extended for enlarging the
contact surface (B and C) during heating material with 1100กษ. (pore is contracted in
reverse direction.) Powder particles are closely attached and the area of surface is
decreased.
Initial binding of particle. The binding between particles are converted to chemical or metallic atomic binding by extrusion.
Growth of contact neck The contact part which bound in 1st step is called to neck, and in this step, the contact surface is extended by the movement of elements around this neck.
Close of pore channel This stage is to give the most change in spatial property of pore in sintering body. It creates isolated pore by closing pore channel which used to be connected between particles.
Globalization of pore The globalization of pore is natural result from the growth of neck, and this is for the minimization of surface energy.
Contraction and termination of pore (Densification) In this step, pore is disappeared or contracted by the movement of materials into the pore.
Coarsening of Pore This is the final stage of sintering, forming larger pore by contracting or disappearing of small and isolated pores.
The main driving force for the above sintering reaction is the decrease of free energy
by the decrease of total surface area of powder compact in resulting from the growth
of particle or the contraction of pore.