The achievement of both high strength and high electrical conductivity in bulk materials is challenging in the development of multifunctional materials, because the majority of the strengthening methods reduce the electrical conductivity of the materials significantly. At room temperature, dislocations have little scattering effect on conduction electrons. Thus, a high density of dislocations can strengthen conductors without significantly increasing the resistivity. However, at room temperature (RT), which is defined as 295 ± 2 K in this paper, deformation can only introduce a limited number of dislocations in pure metals due to dislocation annihilation, i.e. recovery. This limitation is expanded by a well-controlled liquid nitrogen temperature (LNT), which is defined as 77 ± 0.5 K in this paper, deformation process that permits accumulation of both nanotwins and a high density of dislocations accompanied by significantly less recovery than that in RT-deformed samples. The dislocations are organized into refined dislocation cells, with thicker cell boundaries in LNT-deformed samples than those deformed at RT. LNT deformation stores more energy in the material than RT deformation. LNT deformation produces bulk pure Cu with a yield strength about 1.5 times that of RT-deformed Cu. The RT resistivity increase is less than 5% compared with that of annealed Cu.
27 February 2023 in Journal of Materials Research and Technology
Dislocations are responsible for most aspects of plastic deformation in metals. In this work, the dislocation density, ρ, in brass was estimated after different deformation processes via line broadening of X-ray diffractograms using the Convolutional Multiple Whole Profile Program (CMWP) and by Transmission Electron Microscopy (TEM). In addition, we attempted to evaluate, on a global basis, the influence of crystallographic texture in ρ analysis, making sure that the results obtained by XRD could be trusted even in samples with moderate levels of texture. For this, we compared the ρ values for α brass samples (66% Cu and 34% Zn) with different levels of texture, one deformed by cold rolling and the other by equal channel angular extrusion (ECAE).The results suggest that using CMWP program it was possible to satisfactorily estimate the dislocation density in α brass. It also the was shown that the results by XRD and by TEM were self-consistent in two samples texturized to different degrees.
The influence of hot-band grain size and additions of aluminum and manganese on the magnetic properties of non-oriented grain (NOG) low-carbon electrical steel with about 3 wt. (%) Si were investigated using optical microscopy and X ray diffraction. The addition of manganese resulted in larger grains after final annealing. Coarse grains in the hot-band and addition of Mn led to a Goss orientation component after final annealing, which resulted in an increase in the magnetic permeability
1 March 2020 in Journal of Materials Research and Technology
Analysis of dislocation density in metallic materials has been pursued with great interest for many years because dislocations are closely associated with plastic deformation and thus exert a deep effect on the mechanical properties of any material. Crystallographic texture has also a decisive influence in some properties. In this work, the dislocation density was estimated from the line broadening of X-ray diffractograms using the Convolutional Multiple Whole Profile Program (CMWP) and crystallographic texture analyses were performed using inverse pole figures (IPF). The material used in this research was pure copper deformed by cold rolling and Equal Channel Angular Pressing (ECAP). The dislocation density values obtained by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) were compared and discussed. While, in the case of cold rolling, the crystallographic texture of the material was enhanced with increasing deformation, it was reduced with increasing deformation in the case of ECAP processing.