引張変形した Al-Zn-Mg 合金中の水素挙動

Behavior of hydrogen in a tensile-deformed Al-Zn-Mg alloy was investigated by means of hydrogen microprint technique, HMPT, which is a method to visualize location of hydrogen emission from the surface as silver particles. Hydrogen was introduced into the test pieces from one side by cathodic electrolytic charging for 30 min. Then, the test pieces were stretched with continuing the charging, followed by HMPT observation on the other side. Hydrogen evolution was observed on some grain boundaries where the surface relief was formed. Discussion was made considering preferential plastic deformation in precipitate free zones, PFZs, and the geometrical relationship of the boundaries with tensile axis and with slip band inside grains. The results indicated that the shear deformation along grain boundary caused transportation of hydrogen atoms with gliding dislocations to the surface, breakage of surface oxide film, formation of surface relief and then the emission of hydrogen atoms. It was suggested that the preferential deformation in the precipitate free zone was attributed to hydrogen evolution.