Grain Boundary Strengthening

Grain Boundary Strengthening in Strenghtening Process
Decreasing/Finer grain size will increase the yield stress.

The grain size indicates two conditions: The distance for the dislocations have to move to form grain boundary pile-ups and the number of dislocations involved. Having finer grain size, the mobility of the dislocations is harder to move from one grain to another for plastic deformation. In other words, finer grain will impede the dislocations. This will give rise to the strength of the material. However, the grain size cannot be too small (around below 10 nm). This will lead to grain-boundary sliding. The grain boundaries tend to slide and difficult to fit the dislocations in the grain. Thus, less stress required to move them. The equation to this mechanism is The Hall-Petch Equation which states an increase in yield stress is related to a decrease in diameter of the average grain.


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