New principles of increasing strength

Abstract

Dislocations influence the strength of a metal greatly and decrease the resistance to deformation very effectively. However, interacting with each other and with obstacles of another nature, they increase the strength of metals. This makes it possible to represent their shear strength graphically in the form of the U-shaped curve shown in Fig. 1 [ I ]. The dislocation density is depicted along the abscissa and the shear strength is depicted along the ordinate. The minimum strength is determined by some critical dislocation density Pc, evaluated approximately as 107 -l0 s dislocations per I cm 2. This value refers to well annealed metals. Wear hardening in such metals causes an increase in the dislocation density and a simultaneous increase in the resistance to plastic deformation (branch be). This method for increasing the strength is well known and is widely used in practice.However, the strength can be increased efficiently by another method, decreasing the dislocation density (branch ab).