Processing and characterisation of nano crystalline AlCoCrCuFeTi_x high-entropy alloy

Abstract

In this work multi-component equiatomic and non-equiatomic AlCoCrCuFeTi x hexanary highentropy alloys (HEA) was synthesised through mechanical alloying. The prepared powder was sintered via spark plasma sintering. Influence of alloying element variation in the multicomponent system was studied in terms of phase formation and crystal structure by using Thermo-Calc and X-ray diffraction characterization technique (XRD). Particle morphology and chemical analysis studies were carried out through scanning electron microscopy along with Electron Dispersive X-ray Spectroscopy. The crystal structure and nano crystallinity of the hexanary system were recognised using transmission electron microscope (TEM and Selected Area Electron Diffraction [SAED]) while the formation of a solid solution was also studied and discussed. From the XRD and TEM characterisation of 20 h in, milled powders and sintered samples, it was confirmed that the developed HEA system forms a single solid solution BCC phase. The sintered alloy exhibits 97% relative density and an average hardness of 590 VHN.

Effects of Process Control Agent Amount, Milling Time, and Annealing Heat Treatment on the Microstructure of AlCrCuFeNi High-Entropy Alloy Synthesized through Mechanical Alloying

“…of particles leads to the increment of inter-diffusion distance between particles, which reduces the ideal mixture of elements for solid solution formation and postpones the alloying process. Effects of PCA amount on the average crystallite size and lattice strain of the AlCrCuFeNi alloy were calculated using Scherer and Williamson-Hall equations based on the XRD results [28,29] and are presented in Figure 2. It is evident that with increase in PCA amount, crystallite size increases and lattice strain decreases.…”

“…With increase in PCA amount, a decrease in inter-diffusion between particles occurs, which leads to decreased atomic size mismatch between constituent elements, and consequently, decreased lattice strain. In addition, formation of a lubricant layer on the surfaces and decrease in cold welding lead to lower Effects of PCA amount on the average crystallite size and lattice strain of the Al-CrCuFeNi alloy were calculated using Scherer and Williamson-Hall equations based on the XRD results [28,29] and are presented in Figure 2. It is evident that with increase in PCA amount, crystallite size increases and lattice strain decreases.…”

High-entropy alloys fabricated via powder metallurgy. A critical review

“…Since the appearance of PM HEAs, many works were performed to try to analyse the feasibility of these materials as a binder, especially since 2014 ( [47,150,243]) and 2015 [48]. Over the last few months, there has been a dramatic increase in papers dealing with this topic ( [62,129,159,167]). Many of these papers deal with improving the oxidation behaviour [47] or the wear behaviour [131,138,157,243] and the relationship between the fracture toughness and hardness (always in comparison with the conventional cermets/cemented carbides based on Co or Co-Ni).…”

Effects of mechanical activation on chemical homogeneity and contamination level in dual-phase AlCoCrFeNi high entropy alloy

“…Only a small fraction of HEAs are synthesized by solid state processing, although HEAs elaborated this way often exhibit better homogeneity in their microstructures compared to those elaborated using the classical arc melting method [12]. Powder metallurgy has proven to be an alternative way to produce nanostructured HEA with promising properties [13][14][15][16]. However, most of the literature on powder metallurgy synthesis of HEAs reports the use of High Energy Ball Milling in order to reach complete Mechanical Alloying (MA).…”