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Abstract(s)
CoCrFeNi is a well-studied face centered cubic (fcc) high entropy alloy (HEA) that exhibits excellent
ductility but only limited strength. The present study focusses on improving the strength-ductility
balance of this HEA by addition of varying amounts of SiC using an arc melting route. Chromium
present in the base HEA is found to result in decomposition of SiC during melting. Consequently,
interaction of free carbon with chromium results in the in-situ formation of chromium carbide, while
free silicon remains in solution in the base HEA and/or interacts with the constituent elements of the
base HEA to form silicides. The changes in microstructural phases with increasing amount of SiC are
found to follow the sequence: fcc → fcc + eutectic → fcc + chromium carbide platelets → fcc + chromium
carbide platelets + silicides → fcc + chromium carbide platelets + silicides + graphite globules/flakes.
In comparison to both conventional and high entropy alloys, the resulting composites were found to
exhibit a very wide range of mechanical properties (yield strength from 277 MPa with more than 60%
elongation to 2522 MPa with 6% elongation). Some of the developed high entropy composites showed
an outstanding combination of mechanical properties (yield strength 1200 MPa with 37% elongation)
and occupied previously unattainable regions in a yield strength versus elongation map. In addition
to their significant elongation, the hardness and yield strength of the HEA composites are found to
lie in the same range as those of bulk metallic glasses. It is therefore believed that development of
high entropy composites can help in obtaining outstanding combinations of mechanical properties for
advanced structural applications.
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Springer Nature