Evaluation of Grain Boundary Strength through Nanoindentation Technique

A plasticity resistance by a grain boundary was evaluated by nanoindentation measurement in the vicinity of the grain boundary for austenitic stainless steels. Converting a load (P) - displacement (h) relation to a P/h - h curve, the plasticity resistance can be evaluated in the parameter alpha with hardness dimension obtained as the slope on the loading curve. The slope alpha is constant until the plastic zone underneath the indenter reaches to the grain boundary at a certain penetration depth (stage I). and then turns into a higher value in the deeper penetration depth range (stage II). The lower a in the stage I (alpha(I)) means the deformation resistance in the grain interior, and that in the stage II (alpha(II)) includes the deformation resistances of both the grain interior and the grain boundary. Therefore, Delta alpha = alpha(II) - alpha(I) could correspond to the plasticity resistance by the grain boundary. It has been found that the average of Delta alpha is higher for the nitrogen-added sample than that for the nitrogen-free one, suggesting a nitrogen effect including segregation on the plasticity resistance by a grain boundary.

Automated summary

The plasticity resistance by a grain boundary was evaluated using nanoindentation measurement in austenitic stainless steels. It was found that nitrogen addition increased the plasticity resistance at the grain boundary.