TiAl-B合金片状TiB2晶体表面结构及生长机理

SURFACE STRUCTURE AND GROWTH MECHANISM OF TiB2 PLATE IN TiAl-B ALLOYS

  • 摘要: 用原位自生法制备了Ti-54Al-xB (at%)合金并利用XRD,SEM对合金的相组成和微观组织进行了研究。结果表明:片状TiB2基面存在与0001晶向平行的细棒状分枝,表面存在与0001晶向垂直的薄片凸耳状分枝,它们的晶体学取向与母体的取向一致。片状TiB2厚度一般小于0.3μm,表面上的凸耳状分枝厚度一般小于0.1 μm。分析表明,在不平衡凝固条件下,片状TiB2固-液界面前沿产生的富Al边界层和随着片状TiB2晶体的长大导致固-液界面上B原子过饱和度不均匀性增加的共同作用使固-液界面失稳,从而形成了片状TiB2的这种表面结构。

     

    Abstract: Ti-54Al-xB alloys have been produced by an in-situ method. The microstructure and phases constituent of these alloys were investigated by XRD and SEM. The results show that there are needle shape dendrites which are parallel to 0001 on the edge of TiB2 plate and convex flakes which are perpendicular to 0001on the surface of TiB2 plate. These needles or flakes exhibit facets parallel to those of TiB2 plate. It was analyzed that the Al rich layer and inhomogeneity in supersaturation at the solid-liquid interface resulting from non-equilibrium solidification may make the solid-liquid interface unstable, and lead TiB2 plate to forming the surface structure.

     

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