Tailoring the Microstructure and Mechanical Properties of Ta-Alloyed AlCoCrFeNi High-Entropy Alloys

Laves phase-reinforced high-entropy alloys (HEAs) have drawn widespread interest due to their excellent mechanical performance at room/elevated temperatures. In this work, we prepare a few (AlCoCrFeNi)_100-xTa_x (x = 0, 2, 4 and 6) HEAs and assess the effect of Ta on their microstructure and mechanical properties. With increasing Ta addition, their microstructures of the HEAs evolve from a fully body-centered cubic (BCC) microstructure to a hypoeutectic microstructure (primary BCC + eutectic phase). The volume fraction of the Laves phase increases with increasing Ta addition. The strengthening mechanisms of these HEAs are precipitation strengthening and solid solution strengthening. According to an assessment of the contributions of the two strengthening mechanisms, precipitation strengthening dominates the total strength. Moreover, Ta addition cannot transform the fracture mechanisms of these HEAs, which all exhibit brittle fracture.