Deformation microstructures of a low carbon steel with ferrite-pearlite structures have been examined with tritium autoradiography and thermal desorption spectroscopy. The amount of non-diffusible tritium at room temperature increases with strain. When deformed at room temperature which is in the ductile fracture region, the distribution of tritium is fairly uniform within a grain, while it is inhomogeneous when deformed at −80°C which is in the brittle fracture region. In the latter case, the accumulated sites are distributed regularly in arrays and localized as bands. Comparison with slip band traces indicated that the distribution is likely along slip bands. The amount of non-diffusible tritium which desorbs at 180°C is remarkably large when deformed at −80°C. Desorption at 180°C disappears when the deformed sample is annealed at 500°C, suggesting that the defects as the accumulation sites are microdefects presumably point defects or their clusters.
