Amorphization behavior in equiatomic high entropy alloys has been investigated. Pseudo-binary FeCrNi-M-B alloys and true equiatomic high entropy compositions FeCrNi-M-Si (M = Co, Mn, Nb, Ti, Zr) have been synthesized using mechanical alloying. Formation of amorphous phase has been confirmed using X-ray diffraction analysis and transmission electron microscopy. All alloys containing Si showed significant amorphization. Fe80B20 is known to be a good glass former, but no amorphous phase was observed in Fe-B based alloys except for FeCrNiNbB. The slower kinetics of dissolution of B in the alloy due to its sluggish diffusivity caused by its higher melting point is attributed to be the reason for the poor amorphization in B containing alloys. © 2015 Elsevier B.V.