Effect of Heat Treatment on the Microstructure and Microchemistry of Explosive Welded Joints of Ti-5Ta-1.8Nb and 304L SS

Explosive welding process was used for joining Ti-5Ta-1.8Nb alloy to 304L austenitic stainless steel to avoid the formation of intermetallic phases at the interface which otherwise form in fusion welding processes. Both X-ray diffraction and electron microprobe based analysis showed the absence of intermetallic phases at the weld interface within their detection limits. Strain induced phase transformation due to the deformation induced by explosive welding was observed in both the base materials. The 'as received' explosive joints were further heat treated at 873 and 1073 K for durations in the range of 1 to 20 h to select appropriate temperature for further processing subsequent to welding. Detailed analysis using electron microprobe showed considerable microstructural and micro chemical modification at the weld interface due to inter-diffusion of Fe, Ti, Cr and Ni. The width and number of reaction zones varied as a function of heat treatment temperature and time. From the experiments, it was inferred that even the lowest temperature-time combination, i.e. 873 K-1h, is not suitable for heat treatment of explosive joints of Ti-5Ta-1.8Nb/SS 304L, and further lowering of the process temperature is required.