Study On Preparation And Properties Of Al₂O₃/Cu Composites With Three Dimensional Network Structure

Al₂O₃/Cu composites of three-dimensional network structure realizes the network penetration structure of copper matrix and alumina reinforcement. The composite materials can not only realize complementary between the high toughness,ductility,thermal conductivity,conductivity,processing and low density,high hardness,high strength,high temperature resistance,wear resistance and resistance corrosion of Ceramic. But also compared to particles,fiber reinforcement three-dimensional network structure of the metal/ceramic composite material in all directions will can quickly spread and transfer the stress of focusing on the point or the surface in the whole three dimensional space. So that the strengthening effect of the ceramic reinforcement can be increased.In this paper, the Ni coating was prepared by in situ reduction of NiCl₂ on the alumina ceramic surface of the network structure, to improve the wettability of the metal copper and the network ceramics. And using the vacuum vanishing mode casting process, the molten copper is injected into the network ceramics at high temperature. Finely the Al₂O₃/Cu composite material of the three-dimensional network structure is prepared. Then researching organization and micro-structure of the composite interface, and the influence of the volume fraction of ceramic and coating thickness on the mechanical properties of the composites.The results show that: In situ reduction method to prepare the Ni coating with high purity,uniform density and no other impurities. And the coating thickness can be controlled according to the amount of NiCl₂, When the amount of NiCl₂·6H₂O is 45%, the thickness of the coating is about 11μm. Through the vacuum vanishing mode casting method, the copper liquid is filled into the the network ceramic skeleton at high temperature, which the wettability be improved by Ni coating. And closely combined with ceramic reinforcement,Forming the Composite material with three dimensional double phase continuous structure.And it was found that the interface of alumina/copper matrix composites exists solid solution Cu_3.8Ni. It is showed that the Ni coating not only makes the Cu matrix and the ceramic reinforcement produce mechanical bonding, but also forms the combination of dissolution and wetting. The density of the composites decreases with the increase of the volume fraction of the ceramic, which is accorded with the principle of superposition. The bending strength ofthe composites increases first and then decreases with the increase of the volume fraction of the ceramic, When the ceramic volume fraction reaches 27.934%,the bending strength appears the maximum value, Compared to pure metal copper increased by 26% and increased by 46% compared to alumina ceramics; The bending strength of the composites increases with the increase of the coating thickness,when the Ni coating thickness is less than 11.235μm,More than 11.235μm,it will be decrease with the increase of coating thickness; The crack during the bending of the sample extends along with binding surface of ceramic reinforcement and copper matrix,In addition,the proper proportion of reinforcement and matrix can achieve the interlocking effect of the three-dimensional network structure,and make full use of the excellent ductility of Cu matrix and high strength of Al₂O₃,which make the bending strength increase. The tensile strength of the composites decreases with the increase of the volume fraction of the ceramic; The tensile strength of the composites reached the maximum value when the thickness of the Ni coating was about 11μm. The tensile crack first appear in the interface between ceramic and metal, and extend to the ceramic reinforcement.And it was found that the fracture morphology of the interface was the fibers of copper particles and micro holes stretched out and the surface of the ceramic appeared the serrated phenomenon of the copper particles pulled out, Which influence Stress strain curves of composite materials.The resistivity of the composites increases with the increase of the volume fraction of the ceramic phase, and the resistivity reaches 0.146Ωmm, when the volume fraction of the ceramic is 29.241%.