Mechano-chemical synthesis, thermal stability and phase evolution in AlCoCrFeNiMn high entropy alloy

Microstructural Characterization of Mechanically Alloyed FeCoNiMnV High Entropy Alloy Consolidated by Spark Plasma Sintering

“…[31] At this stage, the presence of just a few necks indicates that poor consolidation occurs during the sintering process. In addition, the powder distribution is identical to the initial powders and development of the river-like pattern, [1,11] which is characteristic of the milled powders, can be observed in the microstructure. The increase in the sintering temperature to 700 C results in the higher densification.…”

“…[11][12][13][14][15][16] As an example, although there are several reports on the formation of a single-phase solid solution in the FeCoNiMnCr alloy system, [2,5] the phase separation can occur in the alloy by replacing or adding the constituent elements. Mishra and Shahi [4] have observed that after 20 h of milling, the CrFeMnNiTi alloy could decompose into the FCC, BCC, and sigma phases and the alloy did not show any change in the phases even after vacuum annealing at 700 C. The phase separation was also reported in the AlCoCrFeNi HEA where the addition of Al, as a BCC stabilizer, caused not only a transition from FCC to BCC [1,17] , but also led to the formation of AlNitype and AlNi 3 -type (L1 2 ) phases. [1,11] As mentioned in the literature, one of the most important products of phase separation is the sigma (σ) phase, which is reported in several HEAs containing Fe-Cr and V. [3,16,18,19] The sigma phase, considered as a topologically close-packed (TCP) phase, has a tetragonal structure (space group P4 2 mnm À1 ) that contains 30 atoms per unit cell.…”

“…Mishra and Shahi [4] have observed that after 20 h of milling, the CrFeMnNiTi alloy could decompose into the FCC, BCC, and sigma phases and the alloy did not show any change in the phases even after vacuum annealing at 700 C. The phase separation was also reported in the AlCoCrFeNi HEA where the addition of Al, as a BCC stabilizer, caused not only a transition from FCC to BCC [1,17] , but also led to the formation of AlNitype and AlNi 3 -type (L1 2 ) phases. [1,11] As mentioned in the literature, one of the most important products of phase separation is the sigma (σ) phase, which is reported in several HEAs containing Fe-Cr and V. [3,16,18,19] The sigma phase, considered as a topologically close-packed (TCP) phase, has a tetragonal structure (space group P4 2 mnm À1 ) that contains 30 atoms per unit cell. [3] It has been reported that the sigma phase in the FeCoNiMnCr HEA is formed after annealing at temperatures below 1070 C. [3] Nonetheless, the formation of the sigma phase is affected by annealing conditions as well as the alloying elements.…”

“…It is not, however, a generalized rule for all compositions of HEAs because a single solid solution alloy can be formed only in a few alloy compositions. [1] Equiatomic FeCoNiMnCr, first introduced by Cantor et al, [2] is known as the commencement of producing a single-face centered cubic (FCC)-phase forming HEA. Nevertheless, the experimental evidence on this composition has proved that the formation of the second phase in addition to the solid solution matrix seems to be inevitable.…”

The AC Soft Magnetic Properties of FeCoNixCuAl (1.0 ≤ x ≤ 1.75) High-Entropy Alloys

“…The HEAs are conducive to the formation of a solid solution phase, typically with a structure of a body-centred cubic (BCC) [5,6], a face-centred cubic (FCC) [7][8][9], a hexagonal stacked (HCP) [10,11], or a mixture of the above mentioned structures [12][13][14]. In the past decade, HEAs have drawn extensive attention because of their excellent mechanical and chemical properties, such as great thermal stability [15], good corrosion resistance [16,17], good wear resistance [18], excellent strength [19] and high hardness [20]. Some HEAs show soft magnetic properties due to their ferromagnetic elements such as Fe, Co and Ni [21][22][23][24][25].…”