Effects of Fe addition and addition sequence on carbon inoculation of Mg–3%Al alloy

Abstract

The Mg–3%Al melt was treated by carbon inoculation and/or Fe addition. The effects of Fe addition and addition sequence on the carbon inoculation of Mg–3%Al alloy were investigated in the present study. The role of Fe in the grain refinement of Mg–3%Al alloy treated by carbon inoculation was closely associated with the operating sequence of carbon inoculation and Fe addition. Fe has no obvious effect on the grain refinement of Mg–3%Al alloy by carbon inoculation under the condition that Fe pre-existed in the Mg–3%Al melt before carbon inoculation. However, Fe played an inhibiting role under the condition that the Mg–3%Al melt had been inoculated by carbon before Fe addition. The Al–C–O particles were observed in the sample treated only by carbon inoculation. In addition to Al–C–O particles, Al–C–O–Fe particles could be observed in the sample treated by Fe addition and then carbon inoculation. These Al–C–O and Al–C–O–Fe particles, actually being Al–C and Al–C–Fe phases, should be the potent nucleating substrates for Mg grains, resulting in the grain refinement. However, the Al–C–O–Fe-rich intermetallic particles were mainly observed in the samples treated by carbon inoculation and then Fe addition. The Al–C–O–Fe particles, actually being Al–C–Fe phases, formed under this condition should not be the potent nucleating substrates for Mg grains, resulting in the grain coarsening.