Structural evolution and electrochemical corrosion behavior of Al–Ti–O amorphous-nanocrystalline composite films deposited by magnetron sputtering
By Tian, Shuoshuo; Sun, Kang; Cui, Hongzhi; Xie, Xiang; Wang, Xinzhen; Wei, Na; Wang, Huanhuan; Wang, Weiguo; Song, Xiaojie; Yang, Kezhu
Published in Thin Solid Films
2019
Abstract
Amorphous-nanocrystalline composite films of Al–Ti–O with a range of structures from completely amorphous to nanocrystalline were obtained by magnetron sputtering. The Al–Ti–O films obtained at different temperatures of 100 °C, 200 °C, 300 °C and 400 °C, and then followed by annealing at 500 °C, enabled us to examine the role of substrate temperature and annealing on the microstructure and electrochemical corrosion After annealing at 500 °C, all the structures of the Al–Ti–O films were transformed from amorphous to amorphous-nanocrystalline composite, and Al2TiO5, Al2O3 and TiO2 began to nucleate and grow from the original amorphous phase. At the same time, the film defects such as holes and cracks were reduced and the densities were increased. The variations of roughness and defects of Al–Ti–O films were consistent with the crystallinity trend. Correlated with the nucleation and growth of Al2TiO5, Al2O3 and TiO2 during annealing, the corrosion resistance is significantly enhanced, with a minimum corrosion current density (2.66 nA•cm−2) of two orders of magnitude lower than that of 316L substrate (245 nA•cm−2), when sputtered at 400 °C. This is attributed to the lower galvanic effects between the adjacent phases of amorphous and nanocrystalline composite structures, and also the film with low porosity. The observed phase evolution opens up future design routes for magnetron sputtering oxide films with tunable microstructural and electrochemical corrosion properties.