The H trapping sites which were detected by means of thermal desorption spectrometry were identified by using secondary ion mass spectrometry. High-strength steel specimens were subjected to applied loads in D2O or in 20%NH4SCN solution at 323K. Thermal desorption spectrometry data revealed 2 peaks in the H desorption rate. These corresponded to trap activation energies of between 20.7 and 22.5kJ/mol and between 82.2 and 87.4kJ/mol for the lower-temperature and higher-temperature peaks, respectively. These values were close to the reported 26.8kJ/mol activation energy for desorption from dislocations and to the more than 72.3kJ/mol activation energy for desorption from the interfaces of inclusions and precipitates. By applying secondary ion mass spectrometric image analysis to specimens that had been cooled from the various peak temperatures, it was possible to identify the trapping sites that corresponded to the lower temperature peak. These sites were defects such as dislocations. The sites which corresponded to the higher-temperature peaks were inclusion interfaces, precipitate interfaces, and P segregation bands. The secondary ion mass spectrometry results confirmed that the trapping sites were the same as those which had been deduced, from the trap activation energies, by means of thermal desorption spectrometry.

K.Takai, Y.Homma, K.Izutsu, M.Nagumo: Journal of the Japan Institute of Metals, 1996, 60[12], 1155-62