  A simple fitting approach is introduced for modeling the strength (hardness)
of quaternary and quinary face-centered cubic (fcc) solid solution high entropy
alloys (HEAs) in Co-Cr-Fe-Mn-Ni system. It is proposed that the strength of
solid solution HEAs could be modeled by a polynomial equation where
experimental data are used for finding the coefficients of polynomial. It is
observed that the proposed polynomial could model the strength of solid
solution HEAs very well. Effects of constituent elements on the hardness of
quinary Co-Cr-Fe-Mn-Ni alloys are investigated; the results indicate that the
strength of alloys decreases with increasing the Fe content. The softening
effect of Fe is explained by considering its effect on decreasing the shear
modulus of alloys. Furthermore, the effects of parameters enthalpy of mixing
and valence electron concentration on the strength of HEAs are investigated.
The results show that the enthalpy of mixing has a noticeable effect on the
hardness of quinary Co-Cr-Fe-Mn-Ni alloys and the strength increases with
decreasing the enthalpy of mixing. Furthermore, the results show that hardness
of quinary Co-Cr-Fe-Mn-Ni alloys increases with increasing the parameter
valence electron concentration.
