Scope for improved properties of dissimilar joints of ferrous and non-ferrous metals
(Department of Metallurgy and Materials Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India)
Abstract: Dissimilar joints (DSJs) of ferrous and non-ferrous metals have huge technological importance in the frontiers of new designs in new machineries and improved design of conventional systems. This investigation was undertaken to improve mechanical properties of joints of two dissimilar metals: one is Ti-based and the other is Fe-based. DSJs were processed using bonding pressure from 1 to 9 MPa in step of 2 MPa at 750 °C for 60 min. Properties of the DSJs of these two metals using different mechanisms and methods were compared with the present research for verification. Experimental results from the diffusion bonding mechanism for joining the dissimilar metals validated the improvement in properties. Superior mechanical properties of dissimilar-metals joints were achieved mainly due to the third non-ferrous metallic foil, Ni of ~ 200-mm thickness, which avoided the formation of brittle Fe-Ti-based intermetallics in the diffusion zone. DSJs processed are able to achieve maximum strength of ~560 MPa along with substantial ductility of ~11.9%, which is the best ever reported in the literatures so far. Work hardening effect was detected in the DSJs when the bonding was processed at 5 MPa and above. Bulging ratio of the non-ferrous metal (Ti-based) was much higher than that of the ferrous metal (SS) of the DSJs processed. SEM analysis was carried out to know the details of reaction zone, while XRD was carried out to support the SEM results. Reasons for change in mechanical, physical, and fracture properties of the DSJs with the process parameter variations were clarified.
Key words: diffusion welding; titanium alloy; stainless steel; nickel; interlayer; tensile strength; fractograph