Saran Ramachandran is a Materials Knowledge Exchange Associate at the Advanced Forming Research Centre (AFRC) of the National Manufacturing Institute Scotland (NMIS). His research has been focused on materials joining techniques and mechanical metallurgy investigations required for high-fidelity service applications of welded structures. His current position has offered him a valuable opportunity to lead challenging work packages of rotary friction welding projects funded by tier 1 members of the AFRC, including Rolls Royce and Boeing. Furthermore, he has been awarded an industrial-focused collaborative research and design project jointly funded by the Scottish Funding Council and a continuous casting technology provider named Rautomead.

Dissimilar welds have received a significant attention in a wide range of structural applications as they heavily contribute to light-weighting in transportation industries. However, the welding of dissimilar materials is challenging due to the wide differences in the physical properties of dissimilar materials, particularly in their melting points and thermal conductivities, e.g. where one of the materials attains its melting point much earlier than the other material during fusion welding processes. The result is the formation of defects such as intermetallic phases, porosity, hot cracking, and solidification cracking. Hence dissimilar material welded joints often suffer a reduction in mechanical properties and subsequent early failure under service loading. Solid-state welding processes such as Rotary Friction Welding (RFW) and Friction Stir Welding do not involve the melting of the base materials. Instead, the joining is achieved by the forging action and also due to the friction, which develops severe plastic deformation in the workpiece. Hence the requirement for a lower heat input enables dissimilar materials to be joined without melting, which eliminates many of the drawbacks of the fusion welding processes. Nevertheless, the spiking demands for high-quality dissimilar welds for critical applications such as nuclear, automotive, and aerospace require advanced welding monitoring and control technologies.

My current research at the AFRC focuses on weld parameters optimisation and in-process monitoring of the RFW process to achieve high-quality solid-state welds with zero defects. I have been working towards an approach that enables an intelligent RFW process driven by sensors and data analytics to inspect the quality of dissimilar friction welds in real-time. The dissimilar welds that passed through the NDE inspection regime will be characterised using advanced materials characterisation techniques (ex-situ/in-situ) to understand the material behaviour and structure-property relationships of weld zones (Weld nugget, Thermo-mechanical heat affected zone, Heat affected zone, and Base metal). Overall, my industrial-focussed research at the AFRC will enable me to offer in-depth technical expertise in materials joining processes for successfully delivering commercial and research projects related to RFW.

• Welding of materials with dissimilar properties
• Non-Destructive Evaluation
• In-process weld quality assessment through imaging techniques
• In-situ X-ray imaging
• Quasi Ambient Bonding
• Mechanical metallurgy
• Structure-property correlation
• Sensor-driven Manufacturing
• Metal additive manufacturing

I have a strong background in Materials Engineering, and I have more than eight years of R&D experience in material joining technologies that include Friction Stir Welding, Rotary Friction Welding, Gas Tungsten Arc Welding, and Laser Beam Welding for joining complex dissimilar materials (Magnesium-Titanium and Copper-Stainless steel). Additionally, I also have expertise in materials characterisation, including Optical microscopy, SEM, EDX, EBSD, mechanical testing, and non-contact full-field strain measurement techniques such as Digital Image Correlation (DIC). I have a PhD degree in Mechanical Engineering (Materials joining and Characterisation) which was awarded by the University of Southampton. My PhD research delivered a novel high-fidelity experimental methodology to assess the local material response (stress-strain behaviour) of dissimilar welds using a high-resolution DIC technique. During my Ph.D. research, I have delivered extensive research consultancy services to industry-based clients, which received excellent feedback and income to the University. My postdoctoral research project at the University of Manchester has focused on developing a novel soldering process to enable cost-effective high-temperature Pb-free solder interconnects for microelectronics devices. My postdoctoral research involves an in-depth understanding of materials science alongside the application of material characterisation techniques that include small-scale mechanical testing, in-situ synchrotron X-ray imaging, and Electron microscopy techniques to assess the quality of Pb-free solder joints.