Effects of Y on helium behavior in Ti-Y alloy films

Helium-containing pure Ti and Ti-Y alloy films synthesized by magnetron sputtering method were investigated using techniques of thermal desorption spectrometry (TDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The relevant helium release behavior and microstructure changes were characterized. The mechanical properties of the films were also examined by nanoindentation. It was found that the helium bubbles in the alloy were inclined to be trapped at the interfaces between Y2O3 precipitates and Ti matrix, and there existed a segregation of Y on the surface of the films. Both factors could shift the related TDS peaks to higher temperatures. In addition, the detrimental helium influence on mechanical properties could be suppressed by dispersion of incoherent Y2O3 precipitates in the alloy films, which reduced the sizes of both helium bubbles and matrix grains, and acted as efficient trapping sites for helium bubbles.