An Insight into the Development of Light Weight High Entropy Alloys

Manoj Gupta
2017 Research & Development in Material Science  
Figure 1 : Basic differences in low, medium and high entropy alloys. Evolution of materials is synonymous with the evolution of human civilization from time immemorial. Discovery and development of key materials such as gold, silver, copper, iron, aluminum, silicon, superconductors, and electronic materials has each played a crucial role in ensuring a better life for humans. The discovery and application of alloying and composite technology further diversified the range of properties that can
more » ... realized from different categories of materials specially the metals. In pursuit to discover new materials with enhanced properties, a recent advancement that has captured the attention of researchers worldwide is the discovery of High Entropy Alloys (HEAs) [1, 2] . HEAs are based on a minimum of 5 principal elements unlike the conventional alloys where there is mostly 1 principal element. Five or more elements in HEAs are normally integrated in equiatomic proportion while there are also attempts made on non-equiatomic proportions as well [1, 2] . HEAs exhibit a configurational entropy that is>1.5R (R is gas constant) and as a consequence exhibit a simplified solid solution microstructure rather than characterized by presence of intermetallic compounds ( Figure 1 ). Abstract High Entropy Alloys (HEAs) have been emerged as conceptually innovative alloys that defied the conventional alloying concepts. The concept of HEAs is based on designing the alloys with multiple principal elements ranging from 5 to 35 atomic percent with a target to form single phase solid solution arising from high entropy of the system. The initial development of HEAs was based on the high density principal elements. Recently, low density elements such as Mg, Al, Li, Si and Ca were used to develop light weight high entropy alloy (LWHEA) systems to address the issues related to greenhouse gas emissions. LWHEAs with equiatomic and non-equiatomic compositions were developed successfully. However, single phase solid solution was seldom formed in LWHEAs. In view of current development on LWHEAs, chemical compositions, microstructure and mechanical properties are reviewed and presented in this study.
doi:10.31031/rdms.2017.02.000534 fatcat:ack2ppli3fb5pn5fquebaqrflu