Phase (matter)

Ecology

Biology

Refractory (planetary science)

High entropy alloys

Metallurgy

Materials science

Stability (learning theory)

Computer science

Decomposition

Inorganic chemistry

Thermodynamics

Physics

Organic chemistry

Melting temperature

Diffusion

Elemental analysis

Microstructure

Composite material

Chemistry

Machine learning

Journal of Material Science and Technology

Several body-centered-cubic (BCC) refractory high entropy alloys (HEAs), i.e., HfNbTaTiZr, NbTaTiZr, HfNbTiZr and NbTiZr, were annealed at intermediate temperatures for 100 h, and their microstructures and aging behaviors were studied in detail. All these HEAs start to decompose into multiple phases at around 500 °C, but reenter the single-phase region at significantly different temperatures which were determined to be 900, 1000, 1100 and above 1300 °C for HfNbTiZr, NbTiZr, HfNbTaTiZr and NbTaTiZr, respectively. Our analysis indicates that the onset decomposition temperature in these four HEAs is closely related to the elemental diffusion rates while the ending decomposition temperature is strongly dependent on the elemental melting points. Our findings are important not only for understanding phase stability of HEAs in general, but also for adjusting processing parameters to optimize mechanical properties of these HEAs.

Microstructural stability and aging behavior of refractory high entropy alloys at intermediate temperatures