Stability of ordered L12 and B2 precipitates in face centered cubic based high entropy alloys - Al0.3CoFeCrNi and Al0.3CuFeCrNi2

• DOI: 10.1016/j.scriptamat.2016.06.019
• Publication Date: 2016-06-25T17:30:42Z
• Authors: B. Gwalani; V. Soni; D. Choudhuri; M. Lee; J.Y. Hwang; S.J. Nam; H. Ryu; S.H. Hong; R. Banerjee
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract Adding a small amount of Al to the well-known high entropy alloy (HEA), Al 0.1 CoCrFeNi, to form Al 0.3 CoCrFeNi, leads to the precipitation of highly refined ordered L1 2 precipitates, which are stable at 550 °C. However, the L1 2 precipitates (stoichiometry of (Ni,Cr) 3 (Al,Fe,Co)) are de-stabilized and replaced by coarser B 2 precipitates on annealing at 700 °C. Contrastingly, in the Co-free, Al 0.3 CuCrFeNi 2 high entropy alloy, the L1 2 precipitates are stable at both 550 °C (~ 5 nm) and 700 °C (~ 50 nm), and exhibit a stoichiometry of (Ni,Cu) 3 (Al,Fe,Cr). These results lead to interesting insights into the stability of ordered phases in HEAs as a function of composition and temperature.