钛铸件表面反应层的组成和显微结构的研究

Study on the Composition and Microstructure of the Surface Reaction Layer of Titanium Castings

目的:研究氧化铝系包埋料铸出的钛铸件表面反应层的结构、组成及显微硬度。方法:利用扫描电镜、透射电镜及显微硬度测试仪对用氧化铝系包埋料铸出的钛铸件表面反应层的组成、显微结构及硬度分别进行了检测分析。结果:结果显示氧化铝质铸造模型铸出的纯钛铸件表面反应层共有2层,厚约50μm,最外面为氧化层,厚约为10μm,由Al2O3、MgO、Al2TiO5(Al2O3.TiO2)及TixOy等物质组成;第2层为合金层,厚约为40μm,由Ti3Al和Ti组成,由外向内Ti3Al逐渐减少,Ti逐渐增多。结论:铸件表面反应层的形成机制是当熔融的钛液注入氧化铝系包埋料模型中时,包埋料中的氧化铝以原子态的Al和O存在于熔融钛液中,冷却后生成TixOy和Ti3Al。

Objective： To study the composition and microstructure of the surface reaction layer of titanium cast ings into Al2O3-based investment materials. Methods： The composition, microstructure and hardness of the surface reaction layer of titanium castings were observed by SEM and TEM. Results： There were two layers on the sur face of titanium castings, with outer layer being oxide layer including Al2O3,MgO,Al2TiO5（Al2O3·TiO2） and TixOy. and inner layer being alloy layer including Ti3AI and Ti. Conclusion： The formation mechanism of the surface reaction layer of titanium castings is that, when molten titanium is cast into Al2O3- based casting mould, Al2O3 dissolves into molten titanium by the form of atomic Al and O, Ti3A1 and TixOy are separated out when the melt solidifies.