Outgassing stimulated by deformation

In addition to spontaneous outgassing of materials and desorption stimulate d by particle or photon bombardment, the gas release from mechanically affe cted materials was recently discovered as another source of gas in vacuum s ystems. Particularly outgassing due to operations of manipulators and trans missions becomes a limitation on attaining very low pressures in industrial UHV plants. Earlier studies were concentrated on outgassing during frictio n, this work deals with outgassing when a metallic sample was deformed only , without contact with another body. To study this phenomenon an experiment al device straining a metallic ribbon to provide deform it was installed in an UHV chamber. Another investigation was carried out with a metallic tube closed at one end that was connected to a vacuum chamber and deformed by t wisting. Changes of the total and partial pressures were measured during de formation of a sample and influence of the acting force, deformation (exten sion of the ribbon or angular displacement of the tube), the gas pressure, and the temperature was studied. Results of the measurement led to the conc lusion that hydrogen dissolved in metal, diffusing out when the sample was deformed, represented the main source of the released gases. However, appre ciable amount of gases that could not be supposed to be dissolved in metal was released, too. (C) 1999 Elsevier Science Ltd. All rights reserved.