Ceria Reinforced Copper Matrix Composites Were Prepared By Supercritical Liquid Reduction Technology

The successful development of rare earth oxide doped copper matrix composites has solved the problems of deep processing difficulty and insufficient strength of copper matrix composites to a certain extent,but the current process still has some problems,such as increasing the volume fraction of the second phase will inevitably cause the agglomeration of the second phase particles,resulting in the reduction of toughness and machining performance of copper matrix composites.Therefore,in order to further improve the strength and toughness of copper matrix composites,it is urgent to develop a technology that can obtain fine and evenly dispersed second phase particles in copper matrix composite matrix and ensure that the toughness of copper matrix composites will not be reduced.In this study,a new process was developed to solve the problems of segregation,uneven mixing,easy to produce impurities and low efficiency in the traditional process.The effects of different spray drying processes,heat treatment processes and CeO₂ content on the microstructure and mechanical properties of Cu-CeO₂ composites were studied.Cu-CeO₂ composites with good mechanical properties were prepared by spray drying,supercritical liquid reduction and spark plasma sintering（SPS）.Firstly,the evenly dispersed precursor composite powder was prepared by spray drying,then Cu O-CeO₂ composite powder was prepared by thermal decomposition,and then the oxidized composite powder was reduced in the supercritical liquid reduction system.Finally,the composite material was prepared by SPS sintering.The results showed that the dispersion of the composite powder was better when the concentration of the mixed solution was 10%,the feed rate was 6 ml/min,the inlet air temperature was 200℃,and the outlet air temperature was 115-125℃.The CeO₂ was evenly distributed when the volume fraction of the composite powder was 1%.The particle size of the composite precursor powder calcined at 500℃is smaller and uniform.The composite powder phase reduced at 25 MPa and 380℃is pure,and the copper oxide is completely reduced.The higher the volume fraction of CeO₂,the worse the dispersion of CeO₂ in the composite powder.The Cu-CeO₂ composites with good mechanical properties were prepared by SPS sintering.The interface and mechanical properties of the Cu-CeO₂ composites were studied by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and tensile experiments.The results show that the mechanical properties of Cu-1vol%CeO₂ composites are better with the increase of CeO₂ volume fraction.The main reason is that CeO₂ has the effect of refining grain,and the Cu₂O transition interface is formed between CeO₂ and Cu matrix during the sintering process of SPS,which enhances the interface bonding between CeO₂ and Cu matrix.