Glass formation ability and isothermal crystallization of melt-spun NdNiCuAl ribbons

On the basis of the previous work on (Nd62.5Ni37.5)85Al15 alloy, Cu is selected to partially substitute Ni to form (Nd62.5Ni37.5−xCux)85Al15 (x = 0, 10, 20, 30) melt-spun alloys. The glass-forming ability (GFA) of the as-prepared alloys is evaluated by the isochronal differential scanning calorimeter (DSC) measurement. The results show that GFA increases with Cu content according to several different criterions. The isothermal crystallization behaviors in the corresponding supercooled liquid region is discussed by both Johnson-Mehl-Avrami (JMA) equation and some nucleation and growth models. The fitting shows that it is reasonable to divide the whole crystallization processes into two stages. And the fittings with the nucleation and growth models infers that with increasing Cu content, the nucleation mechanism of the primary stage changes from the quenched-in and steady-state nucleation for (Nd62.5Ni37.5)85Al15, to the steady-state nucleation for (Nd62.5Ni27.5Cu10)85Al15 and (Nd62.5Ni17.5Cu20)85Al15, then to the time-dependent nucleation for (Nd62.5Ni7.5Cu30)85Al15. And the dependence of crystallization mechanisms on Cu substitution agrees well with the change of their GFAs.