Explosive cladding and post-weld heat treatment of mild steel and titanium

• Mild steel/Ti Grade 2 explosive clads were fabricated using a load ratio of 1.07, 2.01 and 3.
• Wavy interface with a sinusoidal pattern was observed for an optimum load ratio of 1.07.
• The clads showed distinct signatures of deformation induced structural changes in the parent metals.
• Formation of intermetallic Fe2Ti phase at the interface was confirmed by TEM.
• Post clad heat treatments have been optimized as 500-550 °C for 10 h.

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.

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