Mechanisms Governing Microstructural Evolution During Consolidation of Nanoparticles
M Tavakol and M Mahnama and R Naghdabadi, MATERIALS AND MANUFACTURING PROCESSES, 30, 1397-1402 (2015).
In micron-scale, powder consolidation process is driven by diffusion phenomenon, while in nano-scale the higher surface energy of particles leads to some anomalous behaviors within the process. In order to investigate the nano-sintering occurrence, an atomistic approach is employed via molecular dynamics simulations. Within this approach, the effect of particle size and temperature is examined. The study of particle structure emphasizes on a transition on the governing mechanism of process depending on the material energy levels. The results show that in a specific particle size at low temperatures, the main sintering mechanism is the plastic deformation, while at elevated temperatures it switches to the surface diffusion. Calculating the sintering activation energy, an anomalous trend is observed with the variations in the particle size. This trend can be described by annihilation of the grain boundary. The identified governing sintering mechanisms are presented in the sintering governing mechanism diagram. The diagram shows that the temperature, at which the main mechanism switches, depends on the particle size. The importance of this finding is that below the switching temperature, increasing time or temperature does not increase the efficiency of the process, significantly.
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