The effects of secondary elemental Mo or Ti addition in Al0.3CoCrFeNi high-entropy alloy on age hardening at 700°C

Three FCC structured high-entropy alloys of Al0.3CoCrFeNi, Al0.3CoCrFeNiMo0.1, and Al0.3CoCrFeNiTi0.1 were synthesized in order to investigate the effects of secondary elemental Mo or Ti addition in Al-0.3 CoCrFeNi alloy on age hardening at 700 degrees C. All of the three alloys exhibited an apparent age hardening, especially when secondary elements were added. The hardness of the Al0.3CoCrFeNi alloy was increased by 65% after aging, whereas the other two alloys displayed an increase of over 80%. The Al0.3CoCrFeNi and Al0.3CoCrFeNiTi0.1 alloys were hardened by massive (Ni,Al)-rich and (Ni,Co,Ti)-rich B2 ordered precipitates, respectively. The large age hardening of the Al0.3CoCrFeNiMo0.1 alloy is attributed to the precipitation of both fine (Ni,Al)-rich phase and heavy blocky (Cr,Mo)(Co,Fe,Ni) sigma phase. (C) 2010 Elsevier B.V. All rights reserved.