MgO和MgAl2O4與純Al間的界面結構特性及其形核作用

MgO和MgAl2O4與純Al間的界面結構特性及其形核作用Interfacial structure of MgO and MgAl2O4 with pure Al and their nucleation behavior

采用掃描電鏡、透射電鏡、X射線衍射等手段研究AlMg合金中常見氧化物MgO與MgAl2O4的異質形核作用。結果表明：高溫下Al熔體與MgO、MgAl2O4發(fā)生化學反應，在接觸界面處生成Al2O3；其中Al/MgO為多步反應，MgAl2O4是其反應的中間產(chǎn)物。反應層Al2O3阻隔液態(tài)Al與MgO、MgAl2O4基底的直接接觸，在一定程度上抑制MgO和MgAl2O4對Al的形核作用。Al/MgO、Al/MgAl2O4界面反應腐蝕原MgO與MgAl2O4的外露晶面，使新生的Al2O3晶粒呈離散化生長。Al/Al2O3、Al/MgO和Al/MgAl2O4形核界面的透射分析結果表明，無論是新生相Al2O3或原MgO與MgAl2O4，均可作為異質相基底觸發(fā)Al的異質形核過程，但具有不同的形核潛力。

The nucleation behavior of common oxides MgO and MgAl2O4 in AlMg alloys were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that, at high temperatures, Al melt would react with MgO and MgAl2O4 substrates to formed Al2O3 at contacting interface. Among them, the reaction of Al/MgO is a multi-step reaction and MgAl2O4 is an intermediate reaction product. The interfacial reaction layer Al2O3 hinders liquid Al from contacting MgO or MgAl2O4 substrates, inhibiting their interfacial reaction to some extent. The interfacial reaction corrodes the exposed planes of original substrates, leading to scattered growth orientations of the new grains. TEM results of three detected nucleation interfaces Al/Al2O3, Al/MgO and Al/MgAl2O4 indicate that either new formed Al2O3 or original MgO and MgAl2O4 could all act as effective heterogeneous substrates to trigger nucleation process of Al, but with different nucleation potencies.

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