Traditionally welding science and technology are associated with joining of metals and alloys as they form a substantial part of the material consumed by mankind. Steels, aluminium alloys, nickel-base super alloys and titanium alloys constitute the major share of these metals and alloys and development in welding science and testing have been in improving the weldability of these materials and for understanding the basic metallurgy of their welds. Similarly, processes employed to weld these materials have been confined predominantly to the arc welding processes and, as in automotive industries, to resistance welding. Today , however, many more new materials and design methods (e.g. multi-material) are available and accordingly the science and technology of joining them have also undergone revolutionary changes.
The need to improve the quality of life, conserve the natural resources, protect the environment etc. has been the major driving force for innovations in the field of materials and their application. Some of these were driven by the desire to take the conventional structural materials like steels, Al alloys etc. up to the upper limits of their performance. Transformation Induced Plasticity (TRIP) steels used in automobile industries, advanced ferritic steels in fossil power plants, super austenitic and super duplex stainless steels for corrosion resistance applications, Al-Li alloys and maraging steels for aerospace applications are successful examples of these innovations. A paradigm shift in the way the materials are chosen for different application is another factor that triggered innovation in this field. The choice of ceramics, composites, fibre reinforced plastic etc. for structural applications, often for very extreme operating conditions, resulted in significant advances and developments in these new structural materials. These materials now find applications in gas turbines (structural ceramics), space vehicles (composites) windmills (composites and fibre reinforced plastics) etc. Development of new technologies, information, communication and bio-technology, triggered the development in a new generation of materials called advanced materials which are used more for their special physical properties like biocompatibility, magnetic, electrical and optical properties.