Grain boundary strengthening of microstructure phases in SS400 structural steel weld zone

Grain boundary strengthening is a method of strengthening materials by changing their average crystalize (grain) size, exhibiting the basic relationship between yield stress and the grain size of the materials. This methodology is based on the observation of grain boundaries that are insurmountable borders for dislocationsand the number of dislocations located within a grain. Applying this methodology to the structural steel weld zone, the mechanical properties of each microstructural phase can be evaluated through the values of grain diameter. For structural steel weld zones, there are not many methods to directly determine the mechanicalproperties of microstructural phases. Thus, in this study, a methodology was created to evaluate the values of the yield stress of materials based on the grain boundary strengthening equation. This method was constructedby observing the average grain size and determining the mechanical properties of three microstructural phasesin the weld zone (i.e. based metal, heat-affected zone, and weld metal). The results from this study provide aneasy way for engineers, architects, and scientists to evaluate the values of mechanical properties of based metal, heat-affected zone, and weld metal in the SS400 structural steel weld zone.