The grain refinement efficiency of Ni-C on Mg-Al alloys

In this article, two kinds of Ni-C alloys which contain flake-like graphite and spherical graphite were prepared and the alloys were added into Mg-Al alloys in order to bring the C element into them. It is found that C can be easily and stably added into Mg-Al alloys. it is considered that the graphite in Ni-C alloys will react with Al in melt to form Al4C3 phase, but the formed Al4C3 will aggregate to the particle-like Al-Ni phase, and these duplex particles are powerful nuclei for alpha-Mg during solidification. It is also found that the morphology of graphite can remarkably influence the refinement. and the refining efficiency of the spherical graphite is much higher than that of the flake-like one. (C) 2008 Elsevier B.V. All rights reserved.