Series of Nanocrystalline NiCoAlFe(Cr, Cu, Mo, Ti) High-Entropy Alloys produced by Mechanical Alloying

Abstract

The mechanical alloying technique was employed to produce series of high entropy alloys, combining in equiatomic percentage Al, Co, Cr, Cu, Fe, Mo, Ni and Ti. Milling times were 0, 10, 20 and 30 h, and experiments were performed in a high energy ball mill (SPEX-8000M) under argon atmosphere. The structural and microstructural changes due to mechanical alloying process were studied by X-ray diffraction and electron microscopy. Although there is the presence of pure elements with HCP crystalline structure, the XRD patterns of as-milled powders revealed the presence of a mixture of nanocrystalline solid solution with FCC and BCC structure phases. The hardness of the powder samples was evaluated by Vickers microhardness testing. The average microhardness values indicate that the alloy with the greatest hardness is the NiCoAlFeMoCr.

Process optimization of high entropy alloys by laser additive manufacturing

“…The powders were generally smooth in texture with no agglomeration and they had particle sizes from about 45 to 106 μm, which resulted in good flowability during deposition. There were different morphologies observed; flake irregular shapes were Cr, Fe, and Ti particles while rounded or fairly spherical shapes were Al, Cu, Ni, and Co particles 49,50 . A gray and white two‐phase contrast in the powder particles of both alloys were observed, which was also reported by Mohanty, et al 51 The white contrast corresponds with the Al, Co, Fe, Ni with a low concentration of Cr and the gray contrast corresponds with the Ti and Cu contents.…”

Alloying, phases and magnetic behaviour of mechanically alloyed FeNiMnCu-based high entropy alloys

“…Accordingly, similar to the FeNiMnCuCo alloy, in FeNiMnCuTi alloy, the FCC phase is more dominant, causing a large powder size after milling. Ti addition has also been reported to increase particle size in NiCoAlFeCuCr alloy [63]. The competition between the welding and fracturing and the hardening rate of initial powders can also affect the final particle size [61].…”

“…A ductile phase and a brittle phase can influence the fracturing and rewelding rates in such a way that particle size is reduced. The mean particle size decreases when hard and brittle elements, such as Mo and Cr, are added [63].…”

Effect of Cr-Doping on the Structural and Magnetic Properties of Mechanically Alloyed FeCoNiAlMn1–xCrx High-Entropy Alloy Powder

“…Similarly, mechanical alloying (MA), a solid-state powder process, is widely used for producing solid solution structures at the nanoscale with unusual properties, 13 being an alternate route instead of arc melting and casting for producing HEAs. 14 Gómez-Esparza et al 15 prepared the FeCoNiAlCr high-entropy alloy powder (HEAP) by MA, and thereafter, 10 h of milling the same has shown a mixture of solid solution phases of FCC and BCC.…”