CRYSTALLIZATION PROCESS AND NON–ISOTHERMAL CRYSTALLIZATION KINETICS OF MELT–SPUN Nd–Fe–B AMORPHOUS THICK RIBBONS

Crystallization processes and non–isothermal crystallization kinetics of Nd6Fe72B22 and Nd6Fe68Ti4B17C5 amorphous thick ribbons rapidly quenched at a roller running rate of 12 m/s were investigated by means of DSC, XRD, Kempen model and Kissinger equation, respectively. Two thick ribbons show different crystallization processes and kinetic mechanisms. The crystallization processes of Nd6Fe72B22 and Nd6Fe68Ti4B17C5 alloys can be discribed as: amorphous phase (AP)→ Nd2Fe23B3→Nd2Fe14B+ α--Fe +Fe3B→Nd2Fe14B+α--Fe+Fe3B+NdFe4B4, and AP→Nd2(Fe, Ti)14(B, C)+α--Fe + Fe3B, respectively. Different from polymorphic crystallization controlled by interface for Nd6Fe72B22 alloy, the crystallization of Nd6Fe68Ti4B17C5 is eutectoidic and the nucleus growth is controlled by diffusion.