Effect of Mg-TiB2 master alloy on the grain refinement of AZ91D magnesium alloy

A novel Mg-50% TiB2 master alloy has been developed by powder in situ synthesis process and its grain refining effect on AZ91D magnesium alloy has been investigated. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) results show the existence of TiB2 particles in this master alloy. After adding 1.8 wt% this master alloy, the average grain size of AZ91D decreased markedly from about 240 mu m to 50 mu m, and the dendritic structure of the primary phase alpha-Mg was obviously refined. Ti and B enriched particles, often observed in the central regions of magnesium grains, are proposed to be the potent nucleating substrates for primary Mg. (C) 2009 Elsevier B.V. All rights reserved.