The generally accepted meaning of the term "sintering," as applied in the metallurgical sense, is the formation of bonds between metal particles, accompanied by a densification of the metal-void system under consideration.
This phase of metallurgy is of considerable practical and fundamental interest. The practical interest stems from the vast volume of powder-metallurgical products being manufactured and the increased use of powder metallurgy in the solution of industrial problems.
The fundamental interest arises from an incomplete understanding of the physical processes involving the atom movements that enable the phenomena of sintering to occur.
In order to study the sintering process, investigators have designed various types of experiments.
These involve the measurement of such parameters as the rate of formation of metal bridges between particles, or the rate of densification of a metal-void compact.
There is considerable argument concerning the relative merits of the various types of sintering experiments.
However, these arguments deal primarily with the problem of whether or not a given experiment is capable of producing information of fundamental significance.
Aside from fundamental considerations, it is necessary to look at the sintering phenomena from a practical viewpoint. Densification studies on powder compacts are particularly useful in providing data that can be used to aid in the evaluation of powder-metallurgical processes.
The densification of a powder compact during sintering may be followed continuously by a dilatometer, or it may be observed in steps by removing specimens from the sintering furnace at given intervals. The dilatometer method and its instrumentation are described in this report. The primary advantages of this method are that it gives a continuous curve and is amenable to autographic recording. The basic information obtained from the dilatometer is the change in length of a powder compact during sintering. The sintering conditions are usually carried out isothermally but, of course, may be conducted non-isothermally.