Single-Phase High-Entropy Intermetallic Compounds (HEICs): Bridging High-Entropy Alloys and Ceramics

TL;DR

This paper reports the fabrication of single-phase high-entropy intermetallic compounds (HEICs) that bridge high-entropy alloys and ceramics, demonstrating their stability, structure, and expanding the family of high-entropy materials.

Contribution

It introduces the first successful synthesis of four- or five-component equimolar B2-phase HEICs and proposes a new phase stability rule for these materials.

Findings

B2-phase HEICs are entropy-stabilized phases.

Single-phase HEICs with high-entropy mixing and anti-site defects were achieved.

Additional D022 phase HEICs were synthesized.

Abstract

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.