Effect of samarium (Sm) addition on the microstructures and mechanical properties of Al-7Si-0.7Mg alloys

The effects of samarium (Sm) additions (0-0.9 wt.%) on the microstructures and mechanical properties of Al-7Si-0.7Mg alloys have been studied in this article. The microstructures of the as-cast samples were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The experimental results indicated that the rare earth Sm affected the secondary dendrite arm spacing (SDAS) ofAl-7Si-0.7Mg alloy. And it was found that Sm had great modification effects on the microstructures of eutectic silicon. When 0.6 wt.% Sm was added to the alloy, the coarse plate-like eutectic silicon was fully modified into a fine fibrous structure; the dendrites of Al-7Si-0.7Mg alloy was best refined. The mechanical properties were investigated by tensile test. The findings indicate that the tensile properties and elongation were improved by the addition of Sm. And a good combination of ultimate tensile strength (215 MPa) and elongation (3.3%) was obtained when the Sm addition was up to 0.6 wt.%. Furthermore the results of thermal analysis reveal that Sm addition had marked effects on eutectic temperature and the latent heat Delta H-R on remelting behavior. (C) 2013 Elsevier B. V. All rights reserved.