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Explosive clads of mild steel (MS) and Ti Grade 2 have been fabricated using different explosive load ratios (R) of 1.07, 2.01 and 3. Interface microstructure, microhardness variation and bond strength of the MS/Ti clad joints were studied as a function of R. A sinusoidal wavy interface of uniform wavelength and amplitude was observed in clads fabricated with R = 1.07, which degraded as the value of R exceeded 2, and was used to select low R values for further fabrication. The presence of martensite and metastable fcc Ti phases in MS and Ti plates respectively has been confirmed by transmission electron microscopy (TEM). Microchemical characterization by electron probe micro analyzer (EPMA) and JMatPro® simulations showed coexistence of intermetallic Fe2Ti and TiC phases at the vortex regions of the wavy interface. The formation of Fe2Ti phase was also confirmed by TEM investigations, although isolated at the vortices of the wavy interface, and hence exert only a minor influence on the bond strength of the 'as clads'. Based on the detailed analysis of interface microstructure and interface bond strength predicted by JMatPro® simulations, the post clad heat treatments for MS/Ti explosive joints have been optimized. [ABSTRACT FROM AUTHOR]

The present investigation deals with the efforts to form a defect free bonded interface between mild steel (MS) and titanium (Ti) using the rotation friction welding process. The conditions were optimized based on several trials by varying friction welding parameters like frictional force, upset force, burn-off length and rotational speed. It has been established that only fine FeTi particles formed in isolated regions at the interface of 'as welded' MS/Ti joints. The evolution of interface microstructure has been studied by diffusion annealing heat treatments in the temperature range of 500-800 °C for a duration of 100 h. Plastic deformation during friction welding reduced the recrystallisation temperature of MS. The variation in microchemistry was measured across the weld interface, which was used as input to predict the formation of various phases and the consequent change in the mechanical properties using the JMatPro® software. Intermetallics were present only as fine isolated particles in bcc-Fe matrix at the interface even after heat treatment at 800 °C for 100 h. The growth kinetics was found to be much slower in friction welded joints as compared to diffusion bonded and explosive clad joints. [ABSTRACT FROM AUTHOR]