where C is a geometric parameter, depending on the type of the boundary. The total stored energy per unit volume, PD, is approximately where G is the shear modulus, b is the Burgers vector and uc is the critical angle for distinguishing between a grain and subgrain boundary (approximately 15°).homogenous strain and the ‘geometrically necessary’
dislocations are the excess of specific Burgers vector related to subgrain boundaries to contribute the local curvature. For deformation at constant strain rate and temperature in commercial Al–1%Mg alloy, rg:rr but for transient deformation, rg is of great significance to describe the evolution of internal dislocation density. Unlike rr, which contributes both to total stored energy and to flow stress, rg mainly contributes to the total stored energy but little to the flow stress.