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Session D33 - Postdeadline Poster Session II.
POSTER session, Monday evening, March 18
Exhibit Hall 2, America's Center
A solid-state phase transformation from Sm_2Fe_17C_x (Th_2Zn_17 structure; x = 0.3, 0.5 and 1.0) Sm_2Fe_14C (Nd_2Fe_14B structure) were studied on ribbons prepared by melt-spinning technique. The phase transformation can be described by the equation \hspace*0.2in Sm_2Fe_17C_1.0 = \delta Sm_2Fe_14C + (1-\delta )Sm_2Fe_17C_y + 3\delta \alpha-Fe. It is found that the process of phase transformation in ribbons melt-spun at high wheel speed (30 m/s) is much faster than that at low wheel speed (7 m/s), while no phase transformation occurs in Sm_2Fe_17C_x ingots prepared by casting (followed by high temperature homogenization). Our results suggest that the reduction of grain sizes by melt-spinning makes the solid-state phase transformation kinetically accessible due to the decreasing diffusion distances and increasing atomic diffusivities.