Formation of interparticle contact resistance in powder materials

Results of an experimental study are presented on interparticle contact formation in fine capillary structures (FCS) upon vacuum sintering. The effect of layers physically absorbed on the surface of the particles on the transport properties of the capillary structure formed is demonstrated with electrical conductivity as an example. Oxide films are studied for their effect on the heat transfer of sintered FCS.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 83–86, October, 1992.     

Powder steel formation under conditions of electric contact compaction

Iron-graphite charge homogenization has been studied under conditions of electric compaction. The optimum technological modes of the formation of powder steel with the bainite structure are found. The effects that the amount of time that pressure was applied and the current passed, the current density, and the compaction pressure have on the homogenization degree of the powder steel is shown. The dependence of the process condition of the quantity of free and fixed carbon is determined. Microstructures of powder steel are presented.     

Electrical conductivity and contact phenomena in porous metallic materials

The change in electrical resistance of copper fiber and powder compacts upon heating from room to the sintering temperature was studied. It was found that different regimes of heating in vacuum did not affect the temperature dependence of electrical resistance. A relationship between electrical conductivity and the relative size of interparticle contacts was derived for a model fiber body. This was in good agreement with data on the tensile strength of real fiber materials.     

异型触头的新成型工艺研究

通过拉丝剪切和冲裁新旧两种成型的工艺路线及相关模具设计的比较，现采用的成型方法满足了这种异型触头的生产，并在效益上占大优势，影响传统的触头生产方法。     

Macroscopic mechanism of formation of interparticle contact in electric current sintering of powders

Conclusions We proposed the mechanism of electric discharge sintering which consists of three stages: the first stage is the formation of the initial contact frame, the second stage is the preferential destruction of a specific volume of the contact frame, and the third stage is the formation of a short-circuited core or of interparticle discrete bridges which close up the interparticle gaps, the increase of the perfection of the contact bridges as a result of consolidation of the central part of the contact bridge, and filling of the resultant voids by the finest particles of electroerosion origin.Translated from Poroshkovaya Metallurgiya, No. 3(315), pp. 33–39, March, 1989.