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烧结是粉末冶金中一个非常复杂的工序。在烧结过程中粉末体的孔隙度要减少,密度要增加。粉末颗粒间的相互粘结和孔隙的被填充都需要物质迁移。本文对烧结过程中粉末体的致密化和物质迁移的扩散机构:体积扩散,表面扩散和晶界扩散,进行了理论上的总结和实验的论证。烧结过程中粉末体内孔隙的消除已有许多实验证明在没有外加应力的情况下,主要是通过体积扩散和晶界扩散进行的。通过钨的表面自扩散的研究,证明当塔曼温度指数小于0.7时起主导作用的物质迁移是表面扩散。并且随着温度的升高体积扩散的作用越来越显著。少量镍对钨的活化烧结和微量硼对 AlNiCo400等磁性材料的活化烧结均证明:烧结过程中的物质迁移主要是通过扩散机构来进行的。烧结是粉末冶金中一个非常重要的工序。它对粉末冶金制品的性能有着决定性的影响。烧结也是一个非常复杂的过程,粉末压坯在烧结过程中要发生许多物理化学的变化。而且在不同的条件下,这些物理化学过程对烧结的影响是不一样的。总的说来,在没有外加压力的情况下,粉末体烧结过程的原动力是系统总表面能的减少。烧结后粉末体的强度要提高,密度要增加,孔隙度要减少。人们对烧结过程进行过不少的研究,提出了模型,由模型推算出了各种公式来描述烧结过程的物质迁移机构,并进行了许多的实验研究。但是,由于烧结过程的复杂性,需要不断地进行科学实验的实践,以揭露和发现烧结过程中的一些规律。本文只对烧结过程中粉末颗粒的相互粘结和致密化过程中的物质迁移机构进行一些理论上的总结和提供一些实验证明。许多实验研究的结果证明:在没有外加应力的条件下,烧结时的物质迁移主要是通过体积扩散、表面扩散和晶界扩散进行的。
Sintering is a very complex process in powder metallurgy. In the sintering process to reduce the porosity of the powder body, the density should be increased. The mutual binding of the powder particles and the filling of the pores require material migration. In this paper, the densification of powder body and the diffusion mechanism of material migration during sintering are discussed: volume diffusion, surface diffusion and grain boundary diffusion. The theoretical summary and experimental proof are given. Elimination of Porosity in Powder Body During Sintering There have been many experiments that show that in the absence of applied stress, bulk diffusion and grain boundary diffusion occur. The study of surface self-diffusion of tungsten shows that the dominant material migration is surface diffusion when the Taman temperature index is less than 0.7. And as the temperature increases, the role of volume diffusion becomes more and more significant. A small amount of nickel on the activation of tungsten sintering and trace boron on the AlNiCo400 and other magnetic materials, sintering and sintering have proved that the material during the sintering process is mainly through the diffusion mechanism to carry out. Sintering is a very important process in powder metallurgy. It has a decisive influence on the properties of powder metallurgy products. Sintering is also a very complicated process, and many physical and chemical changes take place during the sintering of powder compacts. And under different conditions, the impact of these physical and chemical processes on sintering is not the same. In general, the driving force behind the powder sintering process is the reduction of the total surface energy of the system in the absence of external pressure. After sintering the strength of the powder body to be increased, the density should be increased porosity should be reduced. Many people have done a lot of research on the sintering process, put forward a model, deduced various formulas from the model to describe the material migration mechanism of the sintering process, and conducted a lot of experimental research. However, due to the complexity of the sintering process, the practice of scientific experiments needs to be continuously carried out in order to expose and discover some laws in the sintering process. In this paper, we only make some theoretical summary and provide some experimental evidences for the material migration mechanism during the process of sintering and sintering of powder particles. The results of many experimental studies show that material migration during sintering is mainly caused by volume diffusion, surface diffusion and grain boundary diffusion without external stress.