Yukio Inokuti
Research Laboratories, Kawasaki Steel Corp., Chiba 260-0835In order to clarify the crack morphology in 180° bend-forming of Ti films deposited on (011) [100] single crystal of silicon steel and ferritic stainless steel sheets, Ti coating by the hollow cathode discharge (HCD) method was done on polished single crystal and stainless steel sheets, and then the Ti-coated samples were 180° bend-formed and observed by the scanning electron microscope.
Ti-coated silicon steel of (011) [100] single crystal sample showed no distictive crack in Ti films on steel sheet, on which slip lines at intervals of 1~5 mm to the [1210]Ti direction could be observed in a rectangular-like morphology 10~25 mm in width and 20~60 μm in length. Moreover, many fine slip lines at intervals of 50~200 nm to the [0001]Ti direction could be observed.
In contrast, Ti-coated stainless sheel sheet sample showed many highly-curved cracks of 10~50 μm length in a slightly elongated state.
It should be noted that the crack of Ti films differed remarkably depending on the kind of steel sheet, whether the steel substrate was a single crystal and polycrystal. In particular, the Ti films deposited on (011) [100] single crystal of silicon steel showed epitaxial growth with a good coherency relationship between Ti films and the silicon steel matrix.
single crystal of silicon steel, (011) [100], stainless steel sheet, titanium film, crack morphology, 180° bend-forming, slip line, [1210]Ti orientation, coherency