Microstructure, phase formation and hardness investigation of argon arc melted Al-Co-Cr-Fe-Ni and Al-Cu-Cr-Fe-Ni Highentropy Alloys (HEA) with elemental additions / Rafidah Razuan

Traditional alloying is one of the methods to enhance the performance
of pure metals by adding other metals or non-metals. However, as
multiple alloying elements in an alloy may lead to the formation of
many intermetallic compounds with complex microstructures and poor
mechanical properties, new types of metallic alloys called High Entropy
Alloy (HEA) with at least 5 elements with equimolar ratios were developed.
This thesis reports the microstructural studies, mechanical properties
and thermal properties of AlCuCrFeNiTixNby; (x and y= 0.5, 1.0, 1.5),
AlCoCrFeNiZrx; (x= 0.2, 0.4, 0.6, 0.8, 1.0) and AlCoCrFeNiMoxNby;
(x and y= 0.1, 0.2, 0.3) HEAs that have been prepared using Ar
arc melting technique. Effect of adding elements with large atomic
radius, nano precipitate formation and high melting point on the phase
formation, microstructural development and mechanical properties of
HEAs prepared in this study were investigated in detail. Thermodynamic
calculations and structural parameters for HEA phase formation criteria
were carried out and correlated with the experimental results of the HEAs
prepared in this study.