Joining immiscible materials such as copper and stainless steel together is a significant concern due to distinct mechanical and metallurgical properties across the joint line, such as melting points, the coefficient of linear thermal expansion, and thermal conductivity. The joint properties of copper to stainless steel welds are in great demand for various mechanical components of the international thermonuclear experimental reactor, ultra-high vacuum system, plan wave linear-accelerator or linac structure, and heat exchanger. These dissimilar-metals joints offer excellent flexibility in design and production, leading to a robust structure for many cutting-edge applications. Hence, the present article reviews the copper to stainless steel joining mechanism under different solid-state processing conditions. The present understanding says that defect-free strong joints between the dissimilar metals are systematically possible. Apart from this understanding, the authors have identified and highlighted the gaps in the research exploration to date. Moreover, a sustainable methodology to achieve a desirable weld of copper to stainless steel depends on favorable processing conditions.

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Miscible nature of the material is vital to join dissimilar materials together. The wide range of properties within the single structure requires merging of multiple materials. Hence, sustainable welding technology development to join distinct material with extreme immiscibility such as Cu and SS is emerging as a recent research interest. Because of its requirement in nuclear reactors’ critical components, plan wave linac structures and ultra-high vacuum systems. Gas tungsten arc welding is a well-established commercial process. Hence, a study on optimum weld condition to get better quality of Cu to SS bimetallic joint is advantageous and desirable. However, complex flow nature of the molten Cu and SS is a big challenge. Hence, authors have reviewed and discussed the fluid flow of Cu and SS during gas tungsten arc welding. Which, concludes that the flow characteristics of Cu and SS must be studied through experimental and simulations to set up the favourable weld conditions while joining it with gas tungsten arc welding. The mentioned area of interdisciplinary research and not explored yet about the joint’s mechanical and microstructural properties. The said study can potentially predict what will be the final weld properties well before the metallurgical testing. Moreover, the article enlightens the interdisciplinary research aspect of Cu to SS bimetallic joining.

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Keyhole gas tungsten arc welding (K-GTAW) was applied to characterize the weld bead geometry in case of the 6 mm thick electrolytic tough pitch copper. Various conditions of welding speeds and the preheating on the bead on geometry were studied for uniformity of weld geometry. Visual examination, macro bead dimensional analysis, microhardness profile across the transverse section, microstructural analyses were performed to investigate the K-GTAW on electrolytic tough pitch copper. The results revealed that full penetration of 6 mm can be obtained in a single pass using keyhole mode in GTAW. Keyhole length and width were majorly affected by the welding speed and preheating temperature. Significant variations in weld bead geometry were observed even when high heat input conditions were applied without preheating. Uniform weld bead geometry of 5 mm bead width and depth to width ratio of 0.42 was obtained for a length of 80 mm using appropriate preheating of 300°C and heat input condition of 1.37 kJ/mm (resulted from 300 amps welding current, 120 mm/min welding speed and 15.3 volts voltage). In the uniform weld bead geometry, the weld and heat affected zones were consisted of coarse grains relative to base material, wherein the micro hardness variations were observed.