| Abstract Scope |
The first part of the twentieth century led to establishment of a critical resolved shear stress for single crystal plasticity. Then relationship of individual crystal versus polycrystal deformation for face-centered cubic (fcc) aluminum led to a Taylor orientation factor for the ratio of polycrystal-to-single crystal plastic flow stresses, including a parabolic polycrystal stress-strain curve. Work on body-centered cubic (bcc) steel and hexagonal close-packed (hcp) zinc material led to a Hall-Petch inverse square root of grain size dependence for the stress-strain behavior of the fcc, bcc and hcp structures. The grain size dependence is in most constitutive equation descriptions that now include higher strengths for nano-scale materials, also leading to a strength reversal at a grain size of, say, ten nm. Such aspects of polycrystal plasticity relate also to metal hardness properties, including nano-indentation measurements, and to the ductile-to-brittle transition in steel and its fracture toughness. |