Abstract
Behavior of hydrogen that invades pure aluminum, 6061 and 7075 aluminum alloys from two environments, water and hydrogen gas, has been investigated by means of tritium autoradiography, TARG, a technique to visualize the hydrogen atoms in a specimen by using tritium, radioisotope of hydrogen, as a tracer. Sheet specimens of aluminum of 99.99% purity rolled and then annealed, and T6-tempered 6061 and 7075 alloys were subjected to tritium charging in tritiated water and tritium gas, and then to TARG. The TARG was made in the following way. Photographic emulsion was covered on the polished specimen surface, exposed in liquid nitrogen for 14 d, developed, fixed, rinsed and finally observed with an SEM equipped with an EDXS device. In pure aluminum, hydrogen invasion was not detected, while hydrogen was observed in the constituent particles in the two alloys; hydrogen invades 6061 aluminum alloy through Al-Fe-Si phase and 7075 aluminum alloy through Al7Cu2Fe phase. This feature was commonly observed irrespective of the environment, i.e., tritiated water or tritium gas. The number of silver particles detected was larger in 7075 than in 6061.
