Research On The Preparation And Performance Of AIN/Cu-Cr-Zr Composites

Copper and copper alloys are the traditional high-conductivity materials, but its application is greatly restricted because of lack of strength and hardness performance. The development of electronic, mechanical, aeronautic and aerospace industries is in great demand of developing functional materials with high electrical conductivity, thermal conductivity and excellent mechanical properties, low coefficient of thermal expansion.In this thesis, to develop copper matrix composites with high electrical conductivity, high strength and hardness, the components of the composite and the preparation technique were designed. Cu(-Zr) matrix composites were fabricated by mechanical alloying (MA) plus cold pressure forming and repressing and resintering process to find the best fabrication process to meet the high- strength,high-conductivity properties. The mechanical alloying process of powder and the composites microstructure, mechanical, physics properties were systematically observed and analyzed by means of SEM, XRD, TEM, and other test instruments. All of these works lay a solid foundation for developing the utilization area of novel advanced copper matrix composites.Cu (-Zr) supersaturated solid solutions were prepared by mechanical alloying, whereas such a binary system is known to be immiscible in solid and liquid state. The crystalline of Cu-Zr alloy powders were significantly refined and lattice strain had serious lattice distortion during MA process.Densification Process of Cu-Zr alloy powders was studies by means of cold pressing-sintering-repressing-reinterring method. The influence of different composition Cu-Zr composite on the relative density, conductivity, bending strength and hardness was discussed systematically.Compare with the Cu-Zr composite,the hardness of the Cu-Cr-Zr composite was improved because of the smaller of Cr phase and Zr precipitated phases. The addition of a small number of rare earth element-La increased the composite conductivity and the hardness.The hardness was improved obviously after adding ceramic particles AlN. The un-surface treatment of nano-particles AlN was easily reunited due to higher surface energy. The interface between nano-particles and the copper-based material did not close and existed clear gaps.AlN particles were coated Cu by electro-less deposition to modify Cu-AlN interfaces. The results indicate that the interface of composites was compact. The interfacial bonding strength was improved and the loads can be transferred effectively between matrix and AlN by the surface modification with Cu. Therefore, the relative densities, conductivity, bending strength and hardness properties of composites are improved.In this paper, Cu-Zr composite powder was prepared by mechanical alloying process. Cu-Zr composites were formed by cold pressure forming and repressing and resintering method and were compared with Cu-Cr-Zr, Cu-Cr-Zr-La, and Cu-Cr-Zr-La-Al₂O₃ and Cu-Cr-Zr-La-AlN composites to find the best process parameters. The Cu-matrix composites were reinforced by AlN particles. AlN particles were coated Cu by electro-less deposition to modify Cu-AlN interfaces. It is of great significances in theory and practice to develop the new type of copper matrix composites.