Using hardness measurement for dislocation densities determination in FSPed metal in order to evaluation of strain rate effect on the tensile behavior

Hardness indentation size effect led to demonstrate that, multi-pass friction stir processed (FSPed) metal had lower dislocation densities compared to single-pass one. Tensile properties of both specimens were examined in different strain rates and it was indicated that, the lower dislocation densities in multi-pass FSPed metal resulted in more significant alteration in its tensile behavior compared to single-pass FSPed specimen. Yield drop phenomenon also only occurred in highest strain rate of two-pass FSPed metal.