| Ti-Al intermetallic compound thin films were deposited both at room temperature and at elevated substrate temperatures of 573 to 773K by using a two-facing-targets-type DC sputtering system. Atomic compositions of the binary Ti-Al alloy targets are Ti-rich(75Ti-25Al(atm%)), stoichiometry(50Ti-50Al(atm%)) and Al-rich(25Ti-75Al(atm%)). The crystallization processes and phase transformations of Ti-Al thin films were investigated by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The as-deposited films were also annealed successively and isothermally at different annealing temperatures of 773, 873 and 973K. The microhardness of Ti-Al thin films was measured by a dynamic hardness tester. The crystallized phases of as-deposited films, deposited at room temperature and elevated substrate temperatures, were different. Phase transformations during annealing treatment are α-Ti+Ti₃Al→α-Ti+Ti₃Al for Ti-rich films, amorphous/Ti+(Al)→TiAl+Ti₂Al_5+Ti₃Al for stoichiometry and Al+(Ti)/TiAl₂/Ti₂Al_5→α-TiAl₃/Ti₂Al/TiAl₃ for Al-rich films. The analyses of the selected area electron diffraction patterns were in accord with X-ray diffraction results. The above results are discussed in terms of crystallized phases and microhardness. |
|
