ABSTRACT
Pure metals are soft materials. For most engineering applications they cannot provide the required strength. This is the reason alloys were invented. The strength of metals can be increased by alloying and by certain thermal, mechanical or thermomechanical processing. The strengthening mechanisms are simply mechanisms of interaction between dislocations and various obstacles. The major mechanisms are: lattice resistance, strain hardening, solid solution strengthening, grain boundary strengthening and precipitation strengthening. Strengthening in metals can be achieved by impeding the dislocation glide. The strengthening mechanisms are, therefore, related to the interaction between the dislocations and various obstacles present in the microstructure of the material. The mechanical strength of most alloy systems is developed through the operation of several strengthening mechanisms, which operate simultaneously. Alloying elements and material processing plays a key role in the formation of the various obstacles, which are responsible for the operation of these strengthening mechanisms.
