Papers by Keyword: FCC Metal

Abstract: Sheet metal formability is generally affected by crystallographic texture. In particular, bendability and deep drawability of metals and alloys are closely related to the recrystallization texture of the rolled sheets. It is necessary to quantitatively predict them from a viewpoint of texture control. This study proposes a method for simultaneous prediction of both the bendability and the deep drawability on the basis of the average Taylor factor as a polycrystal calculated by using an orientation distribution function. The normalized Taylor factor (M_n-value) and the r-value are used as measures of bendability and deep-drawability, respectively. The predicted results from ideal orientations demonstrated that {001}<uv0> orientation had excellent bendability and poor deep drawability, whereas {111}<uvw> orientation had poor bendability and excellent deep drawability. In addition, the predicted results for practical FCC and BCC metals indicated that cube texture in FCC metals was unfavorable for deep drawing and the γ-fiber texture of <111>//ND in BCC metals was unfavorable for bending.

Abstract: Using electron backscatter diffraction (EBSD), the relationship between deformation textures, developed upon different stress-strain states and characterized by the basic crystallographic orientations of recrystallized grains, has been studied in a FCC metal. The regularities of recrystallization twins development were considered. Crystallo-geometric relations between the deformation and the recrystallization orientations were explained with the mobility of the special grain boundary close to the coinciding site lattice boundary Σ25b. Mechanisms of nucleation and growth of the annealing twins were proposed.

Abstract: The cold-rolling texture of fcc sheet metals with medium to high stacking fault energies is known to consist of the brass {011}<211>, Cu {112}<111>, Goss {011}<100>, S {123}<634>, and cube {100}<001> components. The recrystallization (Rex) texture of cold-rolled Al, Cu and their alloy sheets is well known to be the cube texture. The 40°<111> orientation relationship between the S and cube components, which has been taken as a proof of the oriented growth theory, has made one believe that the S orientation is responsible for the cube Rex texture. The oriented growth theory is claimed to be associated with grain boundary mobility anisotropy. However, some data indicate the Cu component is linked with the cube component. There is no 40°<111> orientation relationship between the Cu and cube components. The strain-energy-release-maximization model (SERM), in which the strain energy due to dislocations is importantly taken into account, suggests that the Cu and S components in the rolling texture are linked with the cube and ~{031}<100> components in the Rex texture, respectively.

Abstract: A stiffening function and a truncated function of the pair-potential of the modified analytical embedded atom method (MAEAM) were suggested for fcc metals. Through fitting the mono-vacancy migration energy, the elastic constants, the cohesive energy and an equilibrium condition of fcc metal crystals correctly, we determined the stiffening parameter and changed the pair-potential parameters and the modification term parameter of the multi-body potential for fcc metals: Ag, Al, Au, Cu, Ir, Ni, Pd, Pt, and Rh. The model calculations fully demonstrate the phonon dispersion curves and the unrelaxed mono-vacancy properties of the nine fcc metals.

Abstract: We explored a new type EAM potential (CLI-EAM) that the value of atomic electron density and pair potential functions are obtained by Chen’s lattice inversion based on first-principles calculations. This EAM potential is applied to Cu, Ag, Cu and Pt metals successfully and the results of basic properties agreed with the experiments. For the same metal, the cohesive energy of fcc structures are the lower than bcc structures.

Abstract: A pseudopotential approach has been used to study the variation of the vacancy formation energy as a function of the parameter of Ashcroft's empty core model potential (AECMP) and nine different exchange and correlation functions (ECF) for some trivalent fcc metals, viz. Al, La, Sc, γ-Ce, Pr and Yb. The criterion used is that should be greater than the Bohr radius ( ). There is a systematic increase in the fitted value of in going from one ECF to another, as follows: KK < Sham < GV < Kle < Harr < VS < Tay < Hub < MD and it is difficult to assign a particular value of for all ECFs for a particular trivalent fcc metal. The inherent simplicity of AECMP makes it difficult to have a universal parameter for all types of atomic property calculations.

Abstract: With the technology advancement, crystal plasticity finite element modeling becomes more and more popular in the simulation of metal forming process. In order to obtain a better understanding of the difference between the Taylor model and finite element model during the simulation of metal forming process, an implicit time-integration procedure with the two polycrystal models is applied in the commercial finite element code ABAQUS to simulate the plane strain compression separately. FCC metal is used in this study. The simulation shows that the two polycrystal models both can predict the compression process approximately. The two modelling results of surface roughness show an agreement with that of the experimental results. However, the side profile calculated by the Taylor polycrystal model is much steeper and straighter than that of finite element polycrystal model. The experimental surface roughness curve shows a high frequency fluctuation. It is much steeper than those of the two models. The simulation results also show that the von Mises stress from the Taylor model is much higher than that of the finite element model.

Abstract: Using pseudopotential approach, vacancy formation energy , different non-split interstitial formation energies and binding energy for the vacancy-impurity pair and that for interstitial impurity over host have been calculated in some cubic fcc metal systems, viz. copper, silver, gold and lead using Ashcroft's potential and Taylor's exchange and correlation function with standard (AT) and fitted to (ATF) and also Heine-Abarenkov’s model potential and same exchange and correlations (HAT). It is difficult to have a universal value for all types of atomic property calculations. The results show that ATF and HAT combinations are better in comparison to AT. Also, the substitutional impurity adjacent to a vacancy is found to be more loosely bound than the interstitial impurity in fcc metals.

Abstract: We show the calculation of the monovacancy formation energy ( v FH E1 ) for three different group-I monovalent fcc metals (Cu, Ag and Au) and two group-IV tetravalent fcc metals (Pb and Th) use a pseudopotential approach. Ashcroft's empty core model potential (AECMP) and nine different exchange and correlation functions (ECF) are used. The variation of v FH E1 with the parameter c r of AECMP for different ECF shows variations with the metals, and c r is observed to be greater than Bohr radius.

Abstract: The present work is devoted to the investigation of the influence of the grain size on the main mechanical characteristics of nanopolycrystals of different metals. The Hall-Petch parameter behaviour for Al, Cu, Ni, Ti and Fe was examined in the wide grain size interval. The stages of plastic deformation and the parameters of work hardening for nanocrystalline copper were analysed in detail. The deformation mechanisms and critical grain sizes accounting for the transition from the dislocation slip to the grain boundary sliding were described.