  High-entropy intermetallic compounds (HEICs) were fabricated by mechanical
alloying and spark plasma sintering to fill a knowledge gap between the
traditional high-entropy alloys (HEAs) and emerging high-entropy ceramics
(HECs). Notably, several four- or five-component equimolar aluminides, such as
the B2-phase (Fe1/5Co1/5Ni1/5Mn1/5Cu1/5)Al, have been made into single-phase
HEICs for the first time. Thermodynamic modeling and a reversible,
temperature-dependent, phase-stability experiment suggest that such B2-phase
HEICs are entropy-stabilized phases. The structure of these HEICs resembles
that of HECs with high-entropy mixing of four or five elements of nearly equal
fractions in one and only one sublattice, but with significant (~10%) anti-site
defects (differing from typical HECs). A new phase stability rule for forming
single B2-phase HEICs is proposed. Five additional HEICs of predominantly D022
phases have also been made. This study broadens the families of equimolar,
single-phase, high-entropy materials that have been successfully fabricated.
