Co dependence of Curie temperature in amorphous Fe-Co-Zr-B-Nb alloys with high glass-forming ability

Effects of Co substitution for Fe on the Curie temperature (T_c), glass-forming ability (GFA) and thermal stability of amorphous Fe _61-xCo_xZr₅B₃₀Nb₄ (FCZBN) alloys were studied for Co content ranging from 0 to 15 at. %. The T_c shows a sinusoid-like behaviour with increasing Co content, revealing two maxima at 3 and 12.5 at. % Co and a minimum at 7.5 at. % Co. Co content dependences of glass transition (T_g), crystallization (T_x) and reduced glass transition temperatures (T_rg) of the amorphous alloys are almost completely opposite to that of the T_c. The T _c decreases with increasing T_g and T_rg, but increases with increasing Co content. The Co content dependence of the T _c is suggested to relate to both Co content and high GFA of the amorphous alloys.