Simulation On The Neck Growth Of The Non-Isometric Biosphere During Initial Sintering

At present, the study on the model of the sintering cell becomes one of the hotspots interiorly and overseas. However, the studies about the model of sintering are mostly focus on the model of the same sphere and only considered single diffusion mechanism. The actual powders have various shapes and the size of particles is in a large range and the process of sintering was effect by the coupling diffusion mechanism in fact. Based on the analysis mentioned above, in this study the non-isometric biosphere model is used to establish the quantitative model during sintering. Not only considering the single surface diffusion mechanism, the single grain-boundary diffusion mechanism and the single volume diffusion mechanism, but also thinking over the condition that the mechanism coupling diffusion mechanisms. The purpose of this investigation is to put forward to the sintering model more close to the actual conditions, to optimize the technology parameters of sinter and provide the gist of basic theory for the preparation of the powder metallurgy products with good integrated performance and their application.Firstly, perfect the sintering neck model of non-isometric biosphere during initial sintering. In this model, respectively studied surface diffusion mechanism, grain-boundary diffusion mechanism and volume diffusion mechanism, especially researched the sinter neck model of coupling this three diffusion mechanisms at last. The Visual C++ was adopt to simulate the change of sintering neck, some factors such as the diameter ratio of two spheres, the sintering time, the sintering temperature and the sintering mechanisms are considered during the simulation. When the relevant parameters are input the dynamic change of sintering neck at different diffusion mechanisms was shown. The sintering neck endlessly become more smooth at the surface diffusion mechanism, the sintering neck not only continue change as line but also the center distance of two spheres contract at the grain-boundary diffusion mechanism, the sintering neck grown with arc and the shrinkage of two centers occurs at the volume diffusion mechanism, the sintering neck of the coupling diffusion mechanism is composed of two arcs with different radius and the shrinkage of two centers occurs as well.Secondly, the effects of the sintering diffusion mechanism, the diameter ratio of two spheres, the sintering temperature and the sintering time on the neck growth and the shrinkage of two centers were examined systematically in the non-isometric biosphere model. With increase of the sintering temperature, the surface diffusion mechanism became the secondary mechanism from the primitively dominant mechanism, while the grain-boundary diffusion mechanism and the volume diffusion mechanism have more contribution to the neck growth gradually and become the dominant mechanisms. When the diameter ratio of two spheres increases, the sintering neck decreases, the shrinkage of two centers increases. In the coupling diffusion mechanism, both the sintering neck and the shrinkage of two centers add when the sintering temperature goes up. In the process of isothermal sintering, with the sintering time move, the center of two grains shrink quickly primarily, then shrinks slowly and at last the shrinkage almost ceases.Thirdly, good agreement of the simulate results in coupling diffusion mechanism with the experimental date from two methods both copper ball and copper powder.At last, the geometry model of three-balls was established too.