| 其他摘要 | Good electrical and thermal conductivities, as well as chemical stability, make copper an attractive material for a wide range of applications, such as heat exchangers, make-and-break electric switches and sliding contact materials and so on. But the lack of strength and the low wear resistance limit the extensive use of pure copper. With the introduction of ceramic particulates, the mechanical properties of Cu can be effectively improved without much loss of electrical conductivity. Layered ternary ceramics possess good electrical and thermal conductivities, low density, high modulus and strength, which promote them to be promising reinforcements for Cu. In the present study, the processing, microstructure and properties of copper matrix composite reinforced by Ti3AlC2 and Zr2Al3C4 particulates were systematically investigated. The aim of the present work is to obtain some insights into the microstructure-property relationship for layered ternary ceramic reinforced Cu matrix composites. The work includes the following aspects:
Firstly, the reaction between Cu and Ti3AlC2 at high temperatures was systematically investigated. At 850oC, Ti3AlC2 reinforcement and Cu matrix were strongly bonded through a 10-nm-thick reaction layer, which composed of TiCx and Cu(Al) solid solution. Above 1000oC, all Ti3AlC2 decomposed into TiCx, which was directly bonded to Cu matrix with low misfit interface. In the light of microstructure observation, we designed two kinds of composites: Ti3AlC2 reinforced and in-situ formed TiCx particles reinforced Cu matrix composites. Then microstructures, electrical resistivity, mechanical and tribological properties of the two composites were studied. As expected, Cu/Ti3AlC2 composites possessed good mechanical properties as well as low electrical resistivity; the mechanical properties of in-situ Cu/TiCx composites were further improved but with some increase of electrical resistivity. Moreover, the sliding and abrasive wear resistance of Cu was obviously improved with the introduction of Ti3AlC2 and in-situ formed TiCx particles, because the loads were effectively born by the reinforcements. Therefore, the tribological mechanism changed and the wear rates reduced dramatically.
Zr2Al3C4 is a conductive ceramic which has higher modulus, strength and hardness than those of Ti3AlC2. The density and electrical conductivity of Zr2Al3C4 is close to that of Ti3AlC2, which endows Zr2Al3C4 to be another attractive reinforcement for Cu. Therefore, a series of Cu/Zr2Al3C4 composite were synthesized and then the microstructure, electrical resistivity, mechanical and tribological properties of the composite were investigated. With the addition of low fraction Zr2Al3C4 reinforcement, the hardness, tensile and flexural strength of Cu were improved without dramatic loss of fracture toughness. In the whole reinforcing range, the electrical conductivity of Cu/Zr2Al3C4 composite was comparable to that of Cu/graphite composite, while the former possessed superior mechanical properties and was fabricated by a much simpler method. The investigation of sliding wear behavior of Cu/Zr2Al3C4 composite against AISI52100 steel demonstrated that the wear mechanism was mild oxidation wear. Therefore, the wear rates of both the composite and the counterpart were very low. Zr2Al3C4 was proven to be promising reinforcement for copper, especially in the field of electrical components.
According to the investigations of Cu/Ti3AlC2, in-situ Cu/TiCx and Cu/Zr2Al3C4 composites, we found that the microstructure, especially the interfacial structure, had significant effects on the mechanical and electrical properties of Cu matrix composites. And the principles for microstructure optimization were proposed. Furthermore, Cu/Nb4AlC3 composite and Ti3AlC2/Zr2Al3C4 hybrid reinforced copper matrix composites were synthesized, which possessed excellent synthetical property. |
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