Progress of non-isothermal sintering methods

DOI: 10.62564/M4-AR1900

Andrii Ragulya

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Valeriy Volodimirovich Skorokhod, great scientist and philosopher of sintering, paid special attention to the influence of heating rate on the sintering of particulate bodies. He was interested in the ideas of V.A. Ivensen concerning the activation of sintering in the case of rapid increase in temperature. Initial work in classical powder metallurgy by V.A. Evensen's theory of non-isothermal sintering was based on experimental observations of the activation of shrinkage at any density, if the temperature of the sample was suddenly increased. These studies were discussed then in the framework of the rheological theory of sintering by V.V. Skorokhod within the framework of the large discussion about the role of defects in the crystal lattice on the activity of the material during sintering. Leading scientists such as Ya. Geguzin, R. German, M. Harmer, Lin-Johnson, M. Ristich, D. Uskokovich, and others paid a lot of attention to the non-isothermal stage of sintering and its theoretical justification. Thus, R. German has modified the model systems of G. Kuczynski’s equations for the non-isothermal case. Lin-Johnson proposed the “Master Sintering Curve” method for analyzing the non-isothermal stage and predicting the best heating regime. M. Harmer hypothesized a rapid overcoming of the temperature range, where the coalescent growth of grains is dominating over shrinkage and proved its validity experimentally. The well-known H. Palmour III, who proposed a method of rate-controlled sintering, has also grounded on Harmer’s hypothesis, and for the first time put the heating rate as a function of the shrinkage rate. Ultrafine and nano-sized powders have stimulated further studies of non-isothermal stage of sintering as it turned out that almost 100% densification occurs during heating and the need for an isothermal stage has decreased. All the above achievements preceded the rapid development of modern methods of sintering under the influence of external mechanical, electrical, magnetic, electromagnetic fields: induction, spark-plasma, microwave, laser and flash sintering, in which the duration of sintering was reduced to tens of seconds or minutes. This rapid development is in progress for now, which ensures the creation of the latest materials and competitive technologies in the world.

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