Challenges of Developing Ductile and Lighter Refractory High Entropy Alloys

Abstract

In the recent past refractory high-entropy alloys (RHEAs) have attracted a lot of attention due to their interesting mechanical properties. These are simple solid solution alloys either with face-centered cubic (FCC) or body-centered cubic (BCC) crystal structures. BCC alloys exhibit relatively higher strengths at high temperatures and therefore, can be considered as structural materials for ultrahigh temperature applications (≥ 1300 ºC). However, the main challenge in developing BCC structured RHEAs for structural applications is balancing their high temperature (HT) strength with their room temperature (RT) tensile ductility and density. Therefore, searching for new and lighter RHEAs with optimized strength and tensile ductility is still a challenge. Improvement of oxidation resistance RHEAs is also an important issue as refractory metals are prone to oxidation in air at high temperatures. This paper describes various theoretical and experimental research works to develop stronger, ductile and lighter RHEAs alloys with novel compositions. The paper also describes various attempts in the development of RHEAs with high creep strength, RT ductility, fracture toughness, lower density, thermo-mechanical fatigue resistance, and host of other physical properties. It will also describe the advance manufacturing techniques in fabricating the components out of these compositions.