Phase and Mechanical Properties Response of the Mechanically Alloyed CoCrFeNiAlX High Entropy Alloys

Abstract

The present work describes the influence of Al content on the CoCrFeNiAl high-entropy alloys prepared by the powder metallurgy technique. The preparation procedure consisted of mechanical alloying and subsequent spark plasma sintering. The content of Al varied from 10 -30 at.% which affected the microstructure and mechanical properties. Using scanning electron microscope (SEM) and X-ray diffraction analysis (XRD) was found the microstructure becomes more grain refined with increasing content of Al accompanied by the annihilation of the ductile FCC solid solution (Cr0.25Fe0.25Co0.25Ni0.25) phase and growth of the brittle and hard BCC solid solution phase (α-Fe) and formation of Al(Co0.5Ni0.5) phases, improving the mechanical properties. The best combination of the porosity, hardness HV 30, and ultimate compressive strength (UCS) was achieved for the studied high-entropy alloy when it contained 20 at. % Al.

Influence of the Mn Content on the Corrosion Behaviour of HEA CoCrFeN-iMnX (X=5, 20, 35 at.%) Prepared via MA+SPS

“…This happens via in-situ reactions during the consequential compaction via SPS. This behaviour has been reported also in previous works [1][2][3][4][5][6], among which the direct contact of the alloy with the graphite die walls is also having a significant role. However, as we are aware, the carbides are homogeneously dispersed throughout the entire crosssection of the compacted alloy favouring the origin of C contamination arising from the PCA.…”

“…The CoCrFeNiMn alloy belongs to the most widely investigated, although it has been almost exclusively prepared either by induction casting or by arc-melting methods, both generating rather coarse-grained microstructures, showing significant heterogeneity. On the other hand, mechanical alloying is fairly used for the preparation of HEAs, except in some of our previous works [2][3][4][5]7]. Among that, the corrosion resistance, either in the aqueous or dry environment, has been largely overlooked.…”