双靶共溅射TiB_2/Al复合薄膜的结构特征与力学性能

Microstructure and Mechanical Properties of TiB_2/Al Composite Films Prepared by Co-sputtering

为研究高分散陶瓷对金属薄膜的强化作用,通过Al和Ti B2靶磁控共溅射方法制备了不同Ti B2含量的铝基复合薄膜,采用X射线能量分散谱仪、X射线衍射仪、透射电子显微镜、扫描透射电子显微镜和微力学探针表征了薄膜的微结构和力学性能。结果表明:在溅射粒子的高分散性和薄膜生长的非平衡性共同作用下,Ti B2靶的溅射粒子被超过饱和地固溶于Al的晶格中,复合薄膜形成的固溶体兼具了置换和间隙2种固溶类型特征。在这种置换和间隙"双超过饱和固溶"的作用下,铝固溶体的晶格产生剧烈畸变,复合薄膜的晶粒在很低的溶质含量下就迅速纳米化,并在晶界区域形成溶质的富集区。随溶质含量的增加,晶界的宽化使复合薄膜逐步形成了极细纳米晶分布于非晶基体中的结构。与此相应,薄膜的硬度迅速提高并在含5.8%Ti B2时达到6.9 GPa的最高值,进一步提高Ti B2的含量,复合薄膜因逐渐非晶态而呈现硬度的降低。研究结果显示了高分散Ti B2的超过饱和固溶对铝基薄膜显著的晶粒纳米化作用和强化效果。

In order to investigate the strengthening effect of highly dispersed ceramics on metal films, TiB2/Al composite films with different TiB2 contents were prepared by magnetron co-sputtering with Al and TiB2 targets. The composition, microstructure and mechanical properties of the films were characterized by X-ray energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy and nanoindentation. The results show that TiB2 are supersaturated in the Al lattice due to high dispersibility of sputtered particles and non-equilibrium growth of the film in sputtering process. The composite film forms supersaturate solid solution which exhibits both substitutional and interstitial features. Because of the dramatic lattice distortion of the ＂dual-supersaturated solid solution＂, the film grains are refined to nanoscale quickly, and the solute is enriched in the grain boundary. With the solute content increasing, the grain boundaries broaden and the composite film gradually forms a two-phase structure in which lower solute content nanocrystals are dispersed in a higher solute content amorphous matrix. Correspondingly, the film hardness increases rapidly and reaches the highest value of 6.9 GPa at 5.8at%TiB2. Then the hardness slightly decreases due to amorphization. The results above indicate the significant refining and strengthening effects of the supersaturated solid solution of highly dispersed TiB2 on aluminum based films.