Synergistic Refining Mechanism Of Mg-3%Al Alloy Refining By Carbon Inoculation Combining With Ca Addition

Mg-3%Al alloy was refined by carbon inoculation combining with 0.2%Ca addition. High grain refining efficiency was obtained and the synergistic refining mechanism was deeply discussed in the present study. Al-C-O particles, actually Al4C3 particles, were formed in the carbon-inoculated Mg-3%Al alloy acting as nuclei for a-Mg grains. Ca addition had no obvious effect on size distribution of the nucleating particles. Ca segregation was proved on Al4C3 particles, which should reduce the interfacial energy of nuclei/Mg. The constitutional undercooling in front of nucleus/liquid was increased from 0.12 degrees C to 0.15 degrees C induced by 0.2%Ca addition. The synergistic grain refining efficiency can be attributed to the higher constitutional undercooling and lower the interface energy of nucleus/Mg induced by Ca addition. More nucleating particles with small size could be activated acting as potent nuclei of alpha-Mg grains. Consequently, Mg-3%Al alloy could be effectively refined due to the synergistic effect induced by carbon inoculation combining with Ca. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University.