A Review on the High Temperature Strengthening Mechanisms of High Entropy Superalloys (HESA)

Abstract

The studies following HEA inceptions were apparently motivated to search for single-phase solid solution over intermetallic phases, accordingly made possible by the concept of high configurational entropy. However, it was realised that the formation of intermetallic phases in HEAs is prevalent due to other criterions that determine stable phases. Nonetheless, recent efforts have been directed towards attributes of microstructural combinations. In this viewpoint, the techniques used to predict microstructural features and methods of microstructural characterisation are elucidated in HESA fields. The study further analyses shortcomings regarding the design approaches of HESAs. A brief history is given into how HESAs were developed since their birth, to emphasize the evaluation techniques used to elucidate high temperature properties of HESAs, and the incentive thereof that enabled further pursuit of HESAs in the direction of optimal microstructure and composition. The theoretical models of strengthening mechanisms in HEAs are explained. The impact of processing route on the HESAs performance is analysed from previous studies. Thereafter, the future of HESAs in the market is conveyed from scientific opinion. Previous designs of HEAs/HESAs were more based on evaluation experiments, which lead to an extended period of research and considerable use of resources; currently, more effort is directed towards computational and theoretical methods to accelerate the exploration of huge HEA composition space.

Molecular Dynamics on Hf-Nb-Ta-Ti-Zr High Entropy Alloy

“…HEAs present a set of superior mechanical properties such as high ductility, toughness, creep, hardness and fatigue resistance when compared to conventional metallic alloys [8]. This outstanding array of physical and mechanical properties [9] opens up possibilities for applications in various fields such as structures [10], refractory [11], cryogenic [12], energy storage [13], biomedical [14], aerospace [15], electrocatalysis [16], among others [17].…”

An Overview of High-Entropy Alloys Prepared by Mechanical Alloying Followed by the Characterization of Their Microstructure and Various Properties

“…These strengthening mechanisms vary with temperature and strain rate [10]. Generally, conventional alloys such as stainless steel are mechanistically designed using solid solution and precipitation strengthening mechanisms [11]. This results in identifying and controlling the various structural phenomena that dictate the alloys.…”

“…As such, the concept of HEAs was not successfully realized for many years. However, contemporary metallurgists have realized the importance of these alloys and developed new grades of HEAs using arc melting, induction melting [8], sputtering, molecular beam epitaxy [9], thermal spray, laser cladding, electrodeposition [10], and mechanical alloying using a high-energy ball mill [11,12]. Overall, mechanical alloying is proven to be one of the best methods for preparing HEAs, which can reduce the burdens of time, energy, and cost as compared with other conventional metallurgical methods.…”

Diseño de aleación de alta entropía de alto desempeño mecánico en condiciones de bajas y altas temperaturas para aplicaciones energéticas y aeroespaciales.

“…La diferencia de tamaño observada y discutida anteriormente se encuentra respaldada por los hallazgos obtenidos por [332,333]. El tamaño de precipitado de la fase γ' se encuentra dentro de los rangos reportados por Ren et al [334] y Joele et al [335]. En la figura 34.a) se puede observar la microestructura resultante del tratamiento termico a 600°C.…”