Effect of Pulsation on Temperature Distribution of Laser-Welded Dissimilar Joint of Thin Sheet

Abstract

Dissimilar joints are characterized by microstructural change and compositional gradient which evolve large variation in physical and mechanical properties across the welded joints. The combination of dissimilar material is challenging goal for development of parts with locally optimized parameter especially for Ti-SS joints. Due to high cost (like Ti-alloy), joining of dissimilar material (Ti-SS) helps to reduce the cost incurred by eliminating the otherwise unavoidable usage of costly and rare metal. The present study includes the pulsed laser welding of dissimilar joint of Ti-alloy and AISI 304. EDX analysis is performed on welded specimen for investigation of morphology attained by different zone. It is reported that fusion zone of dissimilar joint contains very fine-grained morphology because grains are not allowed to grow more at high heat input for shorter time span (pulsation). EDX analysis conveys the presence of intermetallic compounds which is majorly composed of Fe, Ti, and Cr. Cooling rate plays important role to determine microstructural variation. But it is difficult to measure it experimentally, so three-dimensional thermal model has been developed and validated with experimental result. Furthermore, average cooling rate is estimated for Ti and SS at different locations across the weld zone. Significant difference in thermo-physical properties like specific heat capacity and conductivity are major parameter due to which large difference has been found in the estimated cooling rate between Ti-alloy and stainless steel alloy at same location at same instant of time.