2014 Volume 54 Issue 4 Pages 963-969
Effects of cyclic straining on the development of lattice defects were studied in a medium carbon steel containing globular cementite, using thermal desorption analysis (TDA) of post-charged hydrogen that acts as a tracer. The TDA curves were statistically analyzed using Gaussian function in order to separate comprised sub-peaks. The influence of hydrogen pre-charging was further explored. TDA desorption curves were separated into dislocations, grain boundaries, vacancies and vacancy clusters assuming Gaussian distributions for making quantitative comparisons of each defect. Tensile straining of 0.04 readily forms small amount of vacancies. Cyclic straining of 0.004 strain amplitude was more effective in vacancy formation, followed by their clustering. Hydrogen pre-charging before strain cycling was effective in enhancing the formation of those kinds of lattice defects. The maximum fractions of peak areas due to vacancies and vacancy clusters attained in the present study are 21.9% and 6.5% of the total desorption respectively. It was also revealed that the amount of hydrogen in the desorption peak from dislocations increases by straining in the presence of hydrogen. Slow tensile straining was more notable than cyclic straining, while the latter was increased by intensified hydrogen pre-charging.
