Dissimilar Joining of Metals by Powder Metallurgy Route

Abstract

Dissimilar metal joints have a wide range of applications in electronic connectors, due to its physical and mechanical properties. In the present work powder brazing is chosen as a tool for joining of Cu-SS, Cu-Fe, and Cu-Ni. Powder brazing of dissimilar metals has advantages over conventional joining techniques which does not involve melting of the base metal and thus avoids the problems associated with, variation in thermo-physical properties and leads to formation of high amount of undesirable compounds (high intermetallic layer at the joint interface) as a result high joint strength cannot be achieved, an able solutions to produce this type of joints has been developed. In the present work three different types of powder are chosen for brazing, Copper (Cu)-Stainless Steel (SS), Copper-Iron (Fe), Copper-Nickel (Ni) powders. Cu weight (2 gram), stainless steel powder (2 gram), iron powder (2 gram), and Nickel powder (2 gram), then the specimen were compacted with varying loads (4, 5, and 6 tonne), the compacts were in the shape of cylinders. The compacts were sintered at 900 °c in argon atmosphere with a heating rate of (10 k/min), the specimens were cross sectioned using abrasive cutting machine, mounted and polished for macroscopic and microscopic observation. The mounted specimens were polished with emery paper of 1/0, 2/0, 3/0, and 4/0 and were subjected to chemical etching using nital solution. To study macro and microstructures of the specimen optical and scanning electron microscope was used. Form the macrostructures it was observed that there is no presence of cracks in all the joints. It was observed that with the increases in compaction load there is a better bonding between the joints. Microstructures did not show any presence of Intermetallics. Form the hardness data it was confirmed that there is a presence of Intermetallics due to marginal variation in the hardness at the interface in all the cases. From the compression test it was observed that with the Cu-Ni has shown improved strength compared to Cu-SS and Cu-Fe. At higher compaction loads the specimens has shown higher strength in the all the cases (Cu-SS Cu-Fe, Cu-Ni) may be due to better bonding.