Creep Strength of AlCoCrFeNi High-Entropy Alloy Fabricated by Spark Plasma Sintering

In recent years, AlCoCrFeNi High-Entropy Alloy (HEA) has attracted attention because it is expected to be a next-generation aerospace engine material because it has specific strength, excellent corrosion and wear resistance. However, the influence of microstructure of the material synthesized via spark plasma sintering (SPS), a powder metallurgy technique, on high temperature mechanical properties, in particular, creep features, has rarely been reported. In the study, to investigate the abovementioned issue, the HEAs using powder mean size of 14.6, 41.9 and 82.4 μm synthesized via SPS at 1273 K and 1373 K were prepared. Creep tests were conducted at 973 K. The obtained results indicated that HEAs SPSed at 1373 K exhibited higher creep strength than those of synthesized at relatively low temperature, because the microstructure of the former is different from those of the latter. In addition, FCC/B2 phase boundary fracture was observed for HEA synthesized at 1373 K. By contrast, powder boundary fracture was observed for the remaining HEAs. Moreover, the Monkman-Grant relation can be employed to predict creep rupture time for all types of HEAs on one master curve.