Phase equilibria of Sm-Fe-Ti-M (M = Cu, Ag) systems and wetting behavior of M-Sm alloys on SmFe11Ti substrate

Abstract A SmFe12-nXn permanent magnet requires the formation of a suitable grain boundary phase in the microstructure. In this study, Cu and Ag were selected as the major components of the grain boundary phase, and phase equilibria involving the SmFe11Ti phase were investigated. The wettability behavior of the molten grain boundary phase on SmFe11Ti was studied based on this investigation. In the phase equilibria investigation for Fe−Ti−Sm−M (M = Cu, Ag), SmFe11Ti equilibrated Cu−41 mol% Sm and Ag−44 mol% Sm at 1273 K in Cu and Ag systems, respectively. During study of the wetting behavior, molten Cu− 41 mol% Sm alloy that equilibrates with SmFe11Ti exhibited good wettability on the SmFe11Ti substrate, with a final contact angle of 8° at 1133 K. The molten Ag− 44 mol% Sm alloy that equilibrates with SmFe11Ti also exhibited good wettability, with a final contact angle of less than 1° at 1273 K. Although the damage to the SmFe11Ti substrate by Ag- 44 mol% Sm alloy seemed smaller, the difference in the damage to the substrate could not be evaluated between Cu− 41 mol% Sm alloy and Ag− 44 mol% Sm alloy because the Ag−44 mol% alloy wetted the entire substrate and flowed down through the lateral side of the substrate.