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
