Development Of High-Strength And High-Conductivity Copper Matrix Composite Reinforced With Cr₃C₂ Particles

Research on copper matrix materials with high-strength and high-conductivity has been an attractive area in the recent 20 years. The target properties for this kind of material are: tensile strengthσ_b> 600 MPa, micro hardness Hv>180, electrical conductivityσ>80% IACS, and softening temperature Ts>500°C, which could meet the ultra-large-scale integrated circuit lead frame ideal material requests. Researchers from the respect of solid solution strengthening, deformation strengthening, strengthening the grain boundary, precipitation strengthening and composite strengthening in areas for large amount of research.At present, only Japanese Cu-Cr-Zr system and American Al₂O₃/CU system could almost fill these requests and be used practically. It is necessary to establish a set of high-strength high-conductivity copper matrix materials system, which owned by Chinese ourselves. Our research work is just under this background. Trying composite alloy, solid solution, precipitation or deformation strengthening methods on copper matrix material, a set of copper matrix composites reinforced with Cr₃C₂ particles were developed and the reinforced mechanisms for Cr₃C₂/Cu were also discussed. The contents of the thesis are as follows:(1) A new method for Cr₃C₂ particle reinforced Cu matrix material synthesis was proposed on large amount of experiments: electro-arc furnace + graphite crucible isolated from copper crucible fusion technics. The structure and property analysis on the materials showed they had good mechanics and electrical properties.(2) Acute reaction happened between Cr and graphite crucible, which would lead to chromic carbide formation. The chromic carbide was then diffused in copper liquid and Cr₃C₂/Cu was formed later after casting. This kind of reinforced Cr₃C₂ particle formatting mechanism was posted by microstructure analysis.(3) If Cr₃C₂/Cu was prepared with vacuum electro-arc furnace firstly and then spray-formed, after cold reformatting and aging treating the material would have much better good mechanics and electrical properties because of higher solubility and smaller granularity. Cr₃C₂/Cu could obtain the properties as: tensile strengthσ_b=664.5MPa, micro hardness Hv₁₀₀=220, conductivityσ=82.5% IACS, softeningtemperature T_s=550℃, and full fill typical properties requirements for ultra integrated circuit lead frame materials requested. (4) The induction furnace was also used to synthesis Cr₃C₂ particle reinforced Cu matrix material with isolated graphite crucible. Copper mould were designed by ourselves and it could improve the solubility greatly.Furthermore, some relative problems were also discussed:(1) Zn/Cu reaction diffusion study results showed that reaction diffusion coefficient could not be deciphered with Arrhenius equation and the coefficient was 5～7 magnitude greater at 460 C°(2) Depth profile analysis (DPA) is proposed as a new method for the substrate roughness indirect measurement based on Zn/Cu interface study. Roughness definition was applied from two-dimension to three-dimension.(3) Different matters would have different sputtering coefficient and lead to different met allograph. So glow Spectrometer could be used as a new technology in microscopic met allograph observation on the alloy surface, the metallographic metallograph was more detailed and three-dimensional.