Processing effects on the magnetostrictive and physical properties of SmFe2/metal composites

Abstract

Hot pressed SmFe2/Fe and SmFe2/Al composites combine the large magnetostriction of SmFe2 with the mechanical robustness of the Fe or Al matrix. Here we report the dependence of the magnetostriction, density, and mechanical hardness on processing parameters, specifically on the SmFe2 volume fill fraction and the consolidation temperature. The magnetostriction increases monotonically with increasing SmFe2 content, but both the density and hardness decrease; low fill fraction composites are within 10% of theoretical density and have hardnesses of 40–85 Rockwell B, whereas hot pressed SmFe2 powder alone has high porosity (exceeding 30%) and is too soft to register on the Rockwell B hardness scale. The best combination of properties lies in the range of 40%–60% SmFe2. Similar competition between magnetostriction and physical properties is observed as a function of the temperature used to consolidate the samples. The magnetostriction falls slowly as the hot press temperature increases, probably as a result of chemical reaction between the SmFe2 phase and the matrix metal. On the other hand, higher temperature improves the consolidation, resulting in higher density and hardness. These results demonstrate that the magnetostrictive and physical properties of SmFe2 composites can be tailored by adjusting the fill fraction and processing temperature.