Because powders are mostly non-isometric during the sintering process,copper pow-ders were chosen to study the effects of four material transport mechanisms,including surface diffusion,grain-boundary diffusion,volume diffusion,and multi-couplings.These material transport mechanisms were studied with respect to sintering neck growth of a non-isometric biosphere during initial sintering.The evolution of the neck growth in the four transport mechanisms was simulated by Visual C++ as well based on the model of di?erent particles.The results show that the increase of the sintering temperature,both the grain-boundary diffusion and volume diffusion play primary roles in neck growth,while surface diffusion gradually becomes the secondary mechanism.Both the sintered neck and the shrinkage of the two centers increase with increasing temperature by means of the coupling diffusion mechanism.The radius of the sintering neck decreased,and the shrinkage rate of the two centers increased with an increase of the diameter ratio of the two spheres.
Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reac- tion in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al2O3 were studied. The results show that high-energy milling can obviously promote in- ternal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al2O3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al2O3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.
