Study On The Sintering And Densification Mechanism Of Metal/Ceramic Nanocomposite Powders

Cermet is widely used in tool materials .It benefit from the unique properties of the ceremic phase,such as high-strength,high-hardness, antiabrasive, heat-resistant, antioxidant, good chemical stability and so on. On the other hand, cermet also has electric and magnetic properties because of the constituent of the metal phase.So it is used in production of electric resistance and magnetic recording materials in electronic industry.Though,cermet which include magnetic nanoparticles draw more and more attention.In this paper, the nano-Fe/Al₂O₃ composite particles with core-shell structure were prepared from the powder mixture of Al and Fe₃O₄ by mechanochemical method. In the composite particles, Fe nanoparticle is embedded into Al₂O₃ matrix, which prevents the agglomeration and oxidation of Fe nanoparticles.The nano-Fe/Al₂O₃ composite particles is processed in hot-pressed sintering.Through the comparison of results of the XRD analysis,the powder mixtures milled for 6 hours is suitable for sintering.The preliminary sintering process is determined by the test results of DSC analysis of the composite particles.The densification process of hot-pressed sintering and its processing parameters such as sintering temperature, heating rate and holding time were studied in my experiments.Densification is a key process in the sintering. Thus, it is difficult to sinter nano powder because of its unique properties. Simultaneously) it is necessary to avoide the formation of FeAl₂O₄. Out of this consideration, the sintering is complished under Ar atmosphere.The microstructure of those sintered samples were observed by Metallographic microscope,Scanning electron microscope(SEM) and Transmission electron microscopy(TEM).Phase compositions were identified by X-ray diffractometer. The final sintering process is obtained through the procedure above.Vibrating sample magnetometer(VSM) was used to measure magnetic parameters of the samples sintered in different process ,such as coercivity He, saturated magnetization Ms, etc. Also the relationship between the variation regularities of the magnetic parameters and the variation regularities of the processing parameters were studied.