Hi, Grain edge is the boundary of grain from a specific side, a grain boundary is the surrounding edges of the grain while the grain surface either means the apparent surface of the grain under the microscope or the output boundary surface of the grain in a three-dimensional view.

Hope this will help you.

Best wishes.

calized attack at grain boundaries is a function of the 3-dimensional grain boundary structure (5 DOF), and reduced susceptibilities to intergranular corrosion are associated with low energy grain boundaries. The group of low energy grain boundaries comprises low angle grain boundaries, as well as certain high angle grain boundary configurations, such as twin boundaries. Low angle grain boundaries, with misorientations below 15 °, are typically less susceptible to attack than high angle grain boundaries. The resistance of low angle grain boundaries increases with decreasing misorientation, and threshold angles for grain boundary resistance have also been reported

Dear Zahra Kowsar

Determination of the grain size

Yield strength is inversely proportional to the square root of grain size. So, a very small grain size is required since grain size affects hardenability as well as key plastic flow characteristics.

Hall–Petch equation

σy = σo + kd^ -0.5

σy = yield strength

d = average grain size

σo = lattice friction stress and

k = constant (locking parameter)