Phase Transformation of Ti-Al Thin Films by Heating Substrate and Annealing Treatment

摘要

Ti-Al intermetallic compound thin films were deposited both at room temperature and at elevated substrate temperatures of 573 to 773 K 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 percent)), stoichiometry (50Ti-50Al(atm percent)) and Al-rich (25Ti-75Al (atm percent)). The crystallization processes and phase transformation 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 973 K. 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 #alpha#-Ti+Ti_3Al->#alpha#- Ti+Ti_3Al for Ti-rich films, amorphous/Ti+(Al)->TiAl+Ti_2Al_5+Ti_3Al for stoichiometry and Al+(Ti)/TiAl_2/Ti_2Al_5->#alpha#-TiAl_3/Ti_2Al/TiAl-3 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.