Manufacturing of Metal–Diamond Composites with High-Strength CoCrCuxFeNi High-Entropy Alloy Used as a Binder

Abstract

This paper focuses on the study of the structure and mechanical properties of CoCrCuxFeNi high-entropy alloys and their adhesion to single diamond crystals. CoCrCuxFeNi alloys were manufactured by the powder metallurgy route, specifically via mechanical alloying of elemental powders, followed by hot pressing. The addition of copper led to the formation of a dual-phase FCC + FCC2 structure. The CoCrCu0.5FeNi alloy exhibited the highest ultimate tensile strength (1080 MPa). Reductions in the ductility of the CoCrCuxFeNi HEAs and the tendency for brittle fracture behavior were observed at high copper concentrations. The equiatomic alloys CoCrFeNi and CoCrCuFeNi demonstrated high adhesion strength to single diamond crystals. The diamond surface at the fracture of the composites having the CoCrFeNi matrix had chromium-rich metal matrix regions, thus indicating that chromium carbide, responsible for adhesion, was formed at the composite–diamond interface. Copper-rich areas were detected on the diamond surface within the composites having the CoCrCuFeNi matrix due to the predominant precipitation of the FCC2 phase at the interfaces or the crack propagation along the FCC/FCC2 interface, resulting in the exposure of the Cu-rich FCC2 phase on the surface.

The Formation and Phase Stability of A-Site High-Entropy Perovskite Oxides

“…The value of 5ATO-7, 5ATO-8, and 5ATO-9 is 1.609R, while that of 5ATO-10, 5ATO-11, and 5ATO-12 is 1.560R. Rost et al found that the formation of a high-entropy solid solution was affected by the molar fraction of cations, and indicated that the configuration entropy was an important driving force for the formation of a single phase [ 3 ]. According to the concept of high entropy, the value should be higher than 1.609R [ 45 ].…”

“…Since 2004, the research into high-entropy alloys (HEAs) has received great attention due to their vast compositional space and has shown remarkable physical (magnetic and conductivity) and mechanical (strength, hardness and wear resistance) properties [ 1 , 2 , 3 ]. The HEAs were defined as multi-component alloys which were formed by five or more elements with equal or close to equal atomic fractions [ 1 ].…”