利用成分为C^n＋（30mol％）和H^＋（70mol％），加速电压为250kV，脉冲宽度为70ns，束流密度为100A／cm^2的强流脉冲离子束（high intensity pulsed ion beam-HIPIB）辐照DZ4镍基高温合金，辐照次数分别为5、10和15次。利用透射电子显微镜（TEM）分析辐照前后合金表层微观结构的变化。结果显示，与原始样品比较，辐照不同次数后的样品最表面都产生了一层晶粒度为5～10nm的多晶层，它是由DZ4合金中各元素的单质相组成的。在距表面一定深度范围内，不存在γ’相；随着深度的增加，γ’相的含量逐渐增加。
Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with a-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis(EPMA),grazing incidence X-ray diffraction analysis(GIXRD),transmission electron microscopy(TEM), and nanoindentation were used to investigate the characterization of Ti–Al surface alloy. The experimental results show that the thickness of alloy layer is *3 lm, and the content of Al in the *1 lm thickness surface layer is *60 at%. The tetragonal TiAl and TiAl2intermetallics were synthesized at the top surface, which have nanocrystalline structure.The main phase formed in the *2.5 lm thick surface is TiAl, and there are few TiAl2and Ti3Al phase for the alloy.Dislocation is enhanced in the alloyed layer. The nanohardness of Ti–Al surface alloy increased significantly compared with a-Ti substrate due to the nanostructure and enhanced dislocation. Since the e-beam remelted repeatedly, the Ti–Al surface alloy mixed sufficiently with Ti substrate. Moreover, there is no obvious boundary between the alloyed layer and substrate.
Xian-Xiu MeiJian-Qiang FuXiao-Na LiV.P.RotshteinN.N.KovalTeng-Cai Ma
