Mechanical properties of ultra fine-grained HSLA and Ti-IF steels

To study strengthening phenomena in ultra fine structures of metals we employed the MaxStrain system to analyze the correlation between parameters of thermomechanical processing and grain refinement of HSLA and Ti-aided interstitial free steels. The mechanical properties of the investigated, ultra fine-grained steels are a combination of strengthening due to grain boundary, dislocation structures (dislocation arrangement, cell structure) and solid solution. It was found that cell boundaries are more difficult to achieve in HSLA than in Ti-IF steel because of much lower mobility of the dislocations and grain boundaries. An important result is the observation that total strain >5 does not cause any further improvement in the mechanical properties of the investigated steels.