Ca对碳质孕育含Fe的Mg-3％Al合金晶粒细化的“免毒化”作用

摘要

Mg-3％Al alloy was modified by combining Ca addition with carbon inoculation.The effects of Fe addition and addition sequence on the grain refinement were investigated.A higher grain refining efficiency could be obtained for the Mg-Al alloy modificd by combining Ca addition with carbon inoculation.Fe addition and addition sequence had no obvious effect on the grain refinement.Ca addition could effectively avoid grain-coarsening resulting from Fe in the carbon-inoculated Mg-Al alloy.The Al-C-O particles, actually being Al4C3,should act as potent substrates for α-Mg grains in the sample treated by combining Ca addition with carbon inoculation.However,the duplex-phase particles of Al4C3 coated on Al-Fe or Al-C-Fe should be the potent substrates for α-Mg grains if Fe existed in the Mg-Al melt.Ca addition can contribute to the formation of the particles of Al4C3 coated on Al-Fe or Al-C-Fe,regardless of the Fe addition sequence.The poisoning effect of Fe was effectively inhibited in the carbon-inoculated of Mg-Al alloy due to Ca addition,namely,Ca has a poisoning-free effect.%利用Ca和碳质孕育对Mg-3％Al合金进行复合变质处理,并研究了Fe及其Fe的添加顺序对细化效果的影响.与碳质孕育相比,Ca和碳复合孕育后的晶粒细化效果更为显著,Fe及其添加顺序对复合孕育细化效果无显著影响.Ca的添加可有效避免碳质孕育Mg-Al合金中因Fe所导致的晶粒粗化作用.在Ca和碳质复合孕育试样中可观察到大量的Al-C-O颗粒,这些颗粒实际应为Al4C3,并作为α-Mg的形核核心.然而,在熔体中添加Fe后,试样中可观察到大量在Al-Fe或Al-C-Fe表面吸附Al4C3的双相粒子,该双相粒子可作为α-Mg的形核核心并导致晶粒细化.Ca有利于该双相粒子的生存,并与工艺条件无关,从而使得Fe对晶粒细化的“毒化”作用得到有效抑制,即Ca对Fe有“免毒化”效果.