Papers by Keyword: Compound Powders

Abstract: It is a difficult problem how to obtain the density of powder metallurgy products. Sintering billets had been prepared by mechanical milled graphite/copper compound powders firstly. Their microstructures had been analyzed by such means as scanning electron microscope (SEM) and optical microscope. Influence of technological parameters on relative density had also been investigated. The results show that sintering of non-milled powders are intensely affected by sintering temperature, contrary to mechanical milled compound powders. Hot pressed sintering under vacuum can promote densification effectively. By prolonging time, elevating temperature or pressure of hot pressed sintering, relative density of sintering billets can be increased accordingly. Under the same conditions, relative density decreases with mechanical milling time of compound powders.

Abstract: In this paper, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and sintering process were used to characterize Cu-Fe compound powders milled for different times. The increment of defects and the change of granularity, grain size and crystal structure were discussed. Mechanical Alloying (MA) influence on the sintering of Cu-Fe compound powders was analyzed. The results showed that, the refinement of the powders and the increment of defects such as interface and dislocation induced the energy storage. The stored energy released in the sintering process, which reduced the activation energy of vacancy and the activation energy of diffusion. So the sintering temperature was reduced and the structure, strength and hardness of specimens were improved.