Observation of impurity hydrogen evolved from aluminum and titanium alloys during deformation by means of hydrogen microprint technique

Abstract

Hydrogen microprint technique with the aid of photographic effect was applied to pure aluminum and three types of titanium alloys to visualize the hydrogen atoms evolved during tensile deformation. Tensile specimens covered with a monolayer of photographic emulsion were deformed by about 5% at temperatures ranging from -180 to 82°C, subsequently developed and fixed under the safety light in a dark room. Silver grains indicating hydrogen emanation were revealed along coarse slip lines and some grain boundaries, and at second phase (constituent) particles. The density of silver grains was affected by the impurity hydrogen content of the specimen and by deformation temperature. Consequently it can be concluded that hydrogen atoms in the interior of the specimen are transported to the surface with a number of gliding dislocations at room temperature, and that grain boundary becomes a primary diffusion path at elevated temperatures. The newly developed technique with the aid of photographic effect has a higher sensitivity to hydrogen emanation than the conventional hydrogen microprint technique. Moreover, the present technique is by far simpler than tritium autoradiograhy and can be applied to a wide variety of metals and alloys which deform primarily by dislocation glide.