Powder Metallurgy And Sintering Behavior Of Aluminum Copper-nickel Alloy

Copper and copper-based alloys have various applications in the areas of medical, chemical and other engineering application because of their excellent corrosion resistance and high electrical and thermal conductivities. However, to manufacture well performed copper alloy products and explore a new manufacturing route available in the alloy production, the research of copper alloy injection molding has become a hotspot and will provide a platform which allows for consideration of future needs.In this work, Cu-Ni and Cu-Ni-Al alloys have been manufactured via conventional Powder Metallurgy (P/M) and Metal Injection Molding (MIM) techniques respectively. The production process of copper-based alloys, the sintering behavior of the alloy papared by different shaping techniques, and the sintering expansion behavior of Cu-Ni-Al alloy were investigated. A large amount of experimental and theoretical analysis were conducted by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), Elementary analysis and thermal analysis.The traditional sintering process for both P/M and MIM Cu-10Ni alloys involves alloying, homogenization, and densification steps. It is found that the densification and mechanical properties have significant dependence and sensitivity of sintering temperature. The highest density, optimal microstructure and required mechanical performance can be realized by sintering at 1000 and 1050℃for P/M and MIM alloys respectively. Comparing with P/M process, the sintering process of MIM alloy is retarded, and higher suitable sintering temperature is necessary.With the addition of Al, the mechanical properties of copper alloy were significantly improved by alloy strengthening. Superior properties of MIM Cu-10Ni-1.25Al alloy are obtained with the relative density, hardness, tensile strength and elongation of about 97.5%, HV 154, 588MPa and 8.7% respectively. This is a positive precursor to an investigation of MIM process of high performance copper materials.The sintering behavior of Cu-10Ni-1.25Al alloy has been studied and results show that sintering expansion occurs at relative low sintering temperatures while densification process is induced by higher temperatures. It is revealed that Al additive plays the major contribution to the expansion of Cu-10Ni-1.25Al specimens. Because of the high Al additive solubility in Cu and Ni, Al-rich liquid phase was eventually absorbed in Cu matrix and disappeared. The unbalanced diffusion between elements leads to imbalanced mass flow between the solid/liquid interface, resulting in the solid particle grain growth and overall expansion of the specimen. The sintering expansion steps of Cu-Ni-Al alloy involve liquid formation, diffusion, penetration and disappearance. The dimensional change is quantitatively calculated based on phase diagram analysis, and the results show the same expansion rules and calculated numerical values are approach to the actual ones comparing with the experimental measurement in this work. Finally, the comparison of sintering behavior of P/M and MIM Cu-Ni-Al alloy was examined and effects of shaping method on it were elucidated.