Investigation On Microstructure And Performance Of TiC/Cu-Al₂O₃Electrical Contact Material Fabricated

With the rapid development of science and technology, copper and copper alloyplay roles in the development of human society. Copper and copper alloy, which havefetures of high conductivity, high thermal conductivity, excellent ductility and themachinability, are increasingly becoming indispensable metal materials used inmodern industry. However, the low strength and hardness, and the poor wearresistance limit the further application of copper and copper alloy. The TiC/Cu-Al2O3composites combine the high electronic conductivity, thermal conductivity and thegood ductility of Cu, and the high strength and hardness, the low coefficient of thermalexpansion of TiC. Therefore, they are widely used as the switch electric contact, spotwelding electrodes, electronic packaging materials, the rockets throat lining and heatsink materials, etc. In recent years, the TiC/Cu-Al2O3composite have been used in thethe research and application of electrical contact materials, which are becoming moreand more attention.In this paper, TiC/Cu-Al2O3composites have been prepared by powdermetallurgy technology and vacuum hot pressing-oxide sintering with different contentand particle size of TiC. The parameters of the prepared materias are as follows: thesintering temperature,950°C; the compaction pressure,30MPa; the vacuum degree,1.8×10-3Pa; and the time,2hrs. The proporities and microstructures of TiC/Cu-Al2O3composites were tested and observed, as well as the effect of the content and particlesize of TiC on them. The results show that the nano-sized Al2O3, formed by oxidation,evenly dispersed on the copper substrate, and the amorphous layer between TiC andCu enhanced the interfacial bonding strength. Micron grade of TiC particles and nano-sized Al2O3particles all improve the overall performance of the composite materialtogether. The density of TiC/Cu-Al2O3composites are over88%, the microhardnessand conductivity are about151177HV and23.648.8%IACS, respectively.Using the Gleeble-1500D simulator, the true stress-strain curves of TiC/Cu-Al2O3 composites have been investigated. The results indicate that the main process duringthe hot formation of TiC/Cu-Al2O3composites was dynamic recrystallization in whichthe main effective factors were strain ratio and deformation temperature. The thermaldeformation constitutive equation of TiC/Cu-Al2O3composites were worked out basedon the relation among the flow stress, deformation temperature and strain ratio. Andthe processing maps of the TiC/Cu-Al2O3composites were drawn too. Themicrostructures of TiC/Cu-Al2O3composites were observed after compression.Therefore, the best thermal processing parameters of TiC/Cu-Al2O3composites wereachieved.The stress true strain nonlinear equation of TiC/Cu-Al2O3composites wasobtained through nonlinear fitting, and the work hardening rate of composites were gotby derivation of the equation. The work hardening rate was analysised and calculatedto get the dynamic recrystallization critical strain of the composites. The relationshipbetween TiC content, grain size, deformation temperature, strain rate and the effect ofdynamic recrystallization critical strain of composite materials were analyzed. Thedynamic recrystallization critical predicting model of critical strain was determined bythe approached Zener Hollom parameter.