Grain refinement of AZ31 magnesium alloy by new Al-Ti-C master alloys
(Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education,
Shandong University, Ji’nan 250061, China)
Shandong University, Ji’nan 250061, China)
Abstract: New Al4C3-containing Al-Ti-C master alloys (Al-0.6Ti-1C and Al-1Ti-1C) were developed by introducing Ti element into Al-C melt using melt reaction method, in which most of the TiC particles distribute around Al4C3 particles. It is believed that most of the C firstly reacts with Al melt and form Al4C3 particles by the reaction Al(l)+C(s)→Al4C3(s), and after adding Ti into the Al-C melt, the size of Al4C3 particles is decreased and the distribution of Al4C3 is improved through the reaction Ti(solute)+Al4C3(s)→TiC(s)+Al(l). With the addition of 1% Al-1Ti-1C master alloy, the average grain size of AZ31 is reduced sharply from 850 μm to 200 μm, and the grain morphology of α-Mg transits from a fully-developed equiaxed dendritic structure to a petal-like shape. Al-C-O-Mn-Fe compounds are proposed to be potent nucleating substrates for primary Mg. Appropriate addition of Ti is believed to increase the grain refinement efficiency of Al4C3-containing Al-Ti-C master alloys in AZ31 alloy.
Key words: Mg-Al based alloys; grain refinement; Al-Ti-C master alloys; Al4C3; Al-C-O-Mn-Fe compounds