Alloying is considered as the greatest gift for the development of human civilization. Started with serendipitous discovery of Cu-Sn bronze, we have realized the necessity of alloys for every application. From stainless steels in kitchens to the duralumin used in making aircraft, alloys pervade our day to day lives. Most of these alloys have only one or two principal elements, placing restriction on selection of the major elements. In the beginning of the 21st century, the subject of alloys has become a hot topic again, with developments on multi-principal multi-component alloys (MPEAs); alloys with three or more elements in equal or near-equal proportions, removing the restriction on number and the choice of elements and their addition. This includes popular high entropy alloys (HEAs) and relatively medium entropy alloys (MEAs). The field of MPEAs has started in order to ‘expand the compositional space’ as well as ‘explore the unexplored central regions’ of the multi-component systems, chosen from large palette of metals in the Periodic Table. Now, MPEAs and related complex concentrated alloys (CCAs) are considered to be the new ‘avatar’ in physical metallurgy and materials engineering, inspiring novel ideas and approaches to design materials by expanding the compositional space in the multi-component and multi-principal systems and providing unlimited opportunities for new materials development. This has provided the necessary impetus to the physical metallurgy, a ‘new life’ and sustainable research for at least few decades, if not longer.
The present seminar is intended to provide critical analyses of the field, summarizing the principles underlying the birth and growth of these novel materials, progress over last 15 years, the expansion of the field from MEAs to HEAs as well as challenges ahead and possible way forward. The critical analyses of research performed in last one and half decade will be presented with the emphasis on these alloys for potential structural applications to meet the future challenges and mitigating the problems humanity facing today. Taken examples from the literature and present’s own research group, the importance of these materials for various potential structural applications will be provided.