Influence of process control agent and Al concentration on synthesis and phase stability of a mechanically alloyed AlxCoCrFeMnNi high-entropy alloy

Evaluation of high-frequency induction heat sintering and conventional sintering in AlxCoCrFeMnNi high-entropy alloys

“…However, in the Al 1.5 CoCrFeMnNi system, this prediction is not fulfilled since the same phases as the other systems are observed, and the VEC only predicts a BCC phase formation. This behavior can be attributed to the fact that the FCC-BCC region is wider in the Al 1.5 CoCrFeMnNi system than the values calculated by VEC [39]. 31°, so it is difficult to designate which phase corresponds to the precipitates or the matrix through this technique.…”

“…This formation is due to the lower number of electrons in the last orbital of each element that generates higher binding energy for the formation of carbides, in addition to the sintering temperature, which promotes diffusion. In the systems studied, the affinity of the elements present to form bonds with carbon is as follows: Al > Cr > Mn > Fe > Co > Ni, due to the high negative values in the Gibbs free energy [39]. In HFIHS + CS methods, the presence of M 7 C 3 carbides is observed, which have been reported as non-equilibrium carbides.…”

Microstructure and mechanical properties of mechanically-alloyed CoCrFeNi high-entropy alloys using low ball-to-powder ratio

“…The appearance of chromium carbides is related to the usage of nheptane (C7H16) as a process control agent and/or consolidation in a graphite die. Carbides form during the sintering process, and due to diffusion at high temperature, carbon atoms bond with chromium due to their high affinity [40]. This is directly related to the lowest number of valence electrons.…”

“…At least five points from the matrix and five points from the particle of each sample were analysed. In the matrix phase of the S- 40 After annealing, the samples show a more uniform structure without pores detected after sintering.…”

A critical review on mechanically alloyed high entropy alloys: processing challenges and properties

“…Maintaining particle shape and size is usually a difficult job, and milling environments are vital [139,140]. Surface-active materials, usually referred to as process control agents [141], are one of the measures being used to prevent severe welding. These PCA get deposited on the particles' surfaces and significantly lower surface tension [142], limit agglomeration, and interfere with cold welding.…”