• PDF / 646,947 Bytes
• 11 Pages / 593.972 x 792 pts Page_size
• 31 Downloads / 241 Views

DOWNLOAD

REPORT

---

TRODUCTION

THE stored energy in deformed metals is related to the deformation microstructure by a number of structural parameters, including the free dislocation density and the density and magnitude of the dislocation boundaries in the deformed metal.[1] Significant variations in these features have been observed between crystals (or grains, in polycrystalline samples) of different crystallographic orientations and also, in some cases, within crystals/grains of certain orientations.[2–7] A thorough investigation of the stored energy will, therefore, include a microstructural characterization over three different length scales: (1) the sample (polycrystal) scale; (2) the crystal/grain scale (i.e., as a function of crystal orientation); and (3) the local scale (within each crystal/grain). Investigation of the stored energy on these three scales gives important information about both the deformation pattern during plastic deformation, and also provides information for understanding the annealing response during recovery and recrystallization. Measurement of the stored energy on the sample scale can be done with high accuracy by calorimetry.[8] Grain-scale stored energy data has been obtained using either X-ray or neutron diffraction methods based on an analysis of peak broadening.[9,10] In order to obtain information on the local scale, only methods based on an investigation of the microstructure are A. GODFREY, Professor, is with the Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, PeopleÕs Republic of China. Contact e-mail: [email protected] N. HANSEN and D. JUUL JENSEN, Senior Scientists, are with the Materials Research Department, Risø National Laboratory, DK-4000, Roskilde, Denmark. Manuscript submitted September 7, 2006. Article published online August 15, 2007. METALLURGICAL AND MATERIALS TRANSACTIONS A

applicable. Such methods have been outlined in a recent study[11] of the relationship between the stored energy and the reduction during cold-rolling of polycrystalline aluminum. This previous study was focused on the sample scale, allowing a comparison of the stored energy with the flow stress. In contrast, in the present study, we therefore concentrate on an investigation of the stored energy on the crystal/grain and local scales and also in aluminum. For this purpose, in contrast to the previous study, this article, in which a polycrystalline material was used, is focused on the plastic deformation of a set of single crystals of orientations typical of the fcc rolling texture components: {112} (C), {123} (S), and {110} (B). For single crystals, the sample scale, crystal scale, and grain scale are all equivalent. To avoid confusion, therefore, we will use the term ‘‘crystal scale’’ to mean the average stored energy for each single crystal, with the term ‘‘sample’’ referring only to polycrystalline data. The deformation microstructures associated with these three orientations show large differences on both the crystal/grain scale and the local scale.[6,7] Microstruct