This chapter presents the intrinsic mechanisms of dislocation resistance resulting from the forms of interaction and intersections of dislocations occurring during quasi-homogeneous plastic flow, and the evolution of this resistance with straining. This process by itself and in combination with solid solution and precipitation strengthening offers a wide range of possibilities for very significantly increasing the plastic resistance of metals and alloys. In this chapter, only the principal features of the mechanisms in single phase metals and alloys are presented in a low temperature range, where diffusional processes play no role and where the strengthening is unencumbered by other strengthening mechanisms. When lattice resistance is negligible as in pure FCC and HCP metals and in other pure crystalline materials above their characteristic temperatures, strain hardening exhibits common features. While this chapter is primarily devoted to strain hardening in pure FCC metals, these same processes also govern the behavior of BCC metals, alkali halides, metal oxides, and covalent solids. Two types of dislocation resistance are distinguished: the interplane and the intra-plane. Strain hardening manifests itself differently in these two resistances. At larger strains where more than one slip system becomes active, differences in behavior between single crystals and polycrystals become less. FCC crystals can exhibit four stages of strain hardening before hardening saturates at strains of c.a. order 10; these stages are discussed. The temperature and strain rate dependence of the flow stress itself is governed in all stages by dislocation intersections.
Keywords: deformation features, slip systems, FCC crystals, Thompson tetrahedron, stress strain curves, slip distribution, four stages of hardening, sessile locks, dislocation clustering, cell formation
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