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采用扫描电镜、透射电镜、X射线衍射等手段研究AlMg合金中常见氧化物MgO与MgAl_2O_4的异质形核作用。结果表明:高温下Al熔体与MgO、MgAl_2O_4发生化学反应,在接触界面处生成Al_2O_3;其中Al/MgO为多步反应,MgAl_2O_4是其反应的中间产物。反应层Al_2O_3阻隔液态Al与MgO、MgAl_2O_4基底的直接接触,在一定程度上抑制MgO和MgAl_2O_4对Al的形核作用。Al/MgO、Al/MgAl_2O_4界面反应腐蚀原MgO与MgAl_2O_4的外露晶面,使新生的Al_2O_3晶粒呈离散化生长。Al/Al_2O_3、Al/MgO和Al/MgAl_2O_4形核界面的透射分析结果表明,无论是新生相Al_2O_3或原MgO与MgAl_2O_4,均可作为异质相基底触发Al的异质形核过程,但具有不同的形核潜力。
The heterogeneous nucleation of MgO and MgAl_2O_4 in AlMg alloys was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that Al melt reacts with MgO and MgAl_2O_4 at high temperature, and forms Al_2O_3 at the contact interface. Al / MgO is a multi-step reaction and MgAl_2O_4 is the intermediate of the reaction. The reaction layer Al 2 O 3 blocks the direct contact between liquid Al and MgO and MgAl 2 O 4 substrates, and inhibits the nucleation of Al to some extent by MgO and MgAl 2 O 4. The Al / MgO and Al / MgAl_2O_4 interfacial reaction corrodes the exposed crystal planes of the original MgO and MgAl_2O_4 so that the newborn Al_2O_3 grains are discretized and grown. The results of transmission analysis of the Al / Al_2O_3, Al / MgO and Al / MgAl_2O_4 nucleation interfaces show that both the new-phase Al_2O_3 or the precursors MgO and MgAl_2O_4 can be used as heterogenous nucleation sites for heterogeneous phase Al, The nucleation potential.