Morphology and Formation Mechanism of Primary TiB2 in TiAlB Alloys
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摘要: 用原位自生法制备了Ti-53Al-x B合金,并用X射线衍射仪、扫描电镜对合金的相组成和微观组织进行了研究.结果表明:该合金主要由TiAl和TiB2两相组成;初生TiB2呈六面棱柱状,在TiAlB合金凝固过程中,Al原子富集在初生TiB2固-液界面前沿,导致固-液界面上B原子过饱和度不均匀性增加,使固-液界面变得不稳定, 从而在TiB2(0001)面上产生凸台或柱棒状分枝;分枝的各晶面取向与母体的取向一致,在初生TiB2(0001)面的凸台状或柱棒状分枝上能观察到清晰的台阶.Abstract: Microstructure and phase constitution of Ti-53Al-xBalloys produced by an in-situ growing method were investigated by X-ray diffraction and scanning electron microscope respectively. The results show that these alloys are composed of TiAl and TiB2 phase, while the primary hexagonal prism TiB2 exhibits pyramidal protrusion or rod shape dendrites on its basal facets. The protrusions or rods exhibit facets which parallel to that of the primary TiB2. The solid-liquid interface stability of primary TiB2 was discussed and the formation mechanism of the morphology of primary TiB2 was investigated.
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Key words:
- titanium alloys /
- metallic matrix composites /
- boride /
- crystal growth
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