Effects of Mn addition and addition sequence on carbon inoculation of Mg-3％Al alloy

摘要

The Mg-3％ Al melt was treated by carbon inoculation and Mn addition.The effects of Mn addition and addition sequence on the grain refinement were investigated.The effect of Mn on the grain refinement of Mg-3 ％Al alloy by carbon inoculation was closely associated with the operating sequence of carbon inoculation and Mn addition.Mn has no obvious effect on the grain refinement under the condition that Mn pre-existed in the Mg-Al melt before carbon inoculation.However,Mn played an inhibiting role under the condition that the Mg-Al melt had been inoculated by carbon before Mn addition.The Al4C3 particles should act as potent nucleating substrates for Mg grains in the sample treated by carbon inoculation.However,the Al-C-Mn particles with Al4C3 coating film could be observed in the sample treated by Mn addition and then carbon inoculation.These particles with duplex phase structure should also act as potent nucleating substrates for Mg grains,resulting in grain refinement.The nucleating potency of most Al4C3 particles was possibly poisoned by the formation of Al-Mn-rich coating film or the Al-C-Mn intermetallic compound,resulting in grain coarsening in the samples treated by carbon inoculation before Mn addition.