Papers by Keyword: FCC Metals

Abstract: Interatomic potential plays an important role in molecular dynamics simulation, which determines both the efficiency and accuracy of the simulations. Lattice inversion is a method which can be used to develop interatomic potential from first principle results directly. In present work, a robust potential model based on lattice inversion is proposed. Then the potential model is applied to develop interatomic potentials for eight common FCC metals. The cohesive energy curves calculated using first principle calculations can be well reproduced, which verifies the reliability of the developed potential. Additional physical properties, including equilibrium lattice constant and cohesive energy, elastic constants, are predicted and found reasonable agreement with corresponding first principle results.

Abstract: The study of the role of various factors in plastic behavior of materials is carried out using a mathematical model that takes into account fundamental properties of deformation defects in a crystal lattice based on the continuum theory of dislocations. Calculations were performed for copper, nickel, aluminum, and lead using a specialized software system Dislocation Dynamics of Crystallographic Slip. It has been shown that a decrease in the density of dislocations from 10¹² m^-2 to 10¹¹ m^-2 leads to an increase in the dislocation path in 10−16 times, and the maximum velocity in 1.5−2 times in copper and nickel, by nearly 20% in aluminum, and practically remains unchanged in lead. A decrease in the lattice and impurity friction from 2 MPa to 0.1 MPa leads to a linear increase in the path and the maximum velocity of the dislocation by 10−25%.

Abstract: History of loading is the result of interaction of the material microstructure evolution and the loading conditions. The present work aims at an investigation of the behavior in face-centered cubic (FCC) metals under loading with a strain rate jump at different stages. In order to describe the behavior of FCC metals under loading we propose a mathematical model. This model is based on a system of ordinary differential equations (ODEs) and realized as software.

Abstract: Equal channel angle pressing (ECAP) of commercial purity aluminum (1050), oxygen free high conductivity copper (OFHC Cu) and high purity tin (99,99% Sn) were conducted using C processing route. The variation of microstructure, of micro-Vickers hardness and of macroscopic material parameters with number of pressings was documented up to ten passes. Tensile tests were used to evaluate post ECAP deformation response. Optical microscope was used to obtain statistical information on the microstructure developed during ECAP. The present results showed that, as it can be found in the literature, first ECAP pass has resulted in enhancement of mechanical properties. Further ECAP processing, as original observation, has resulted in slight improvement and after ~7 pressing decreasing of hardness can be observed. The true stress–strain curve for ECAP-ed specimens tested under tension showed the evolution of macroscopic material properties is similar. This behavior can be connected with the deformation microstructure of the specimen, grain deformation and fragmentation.

Abstract: A Brief Sketch of Different Models for the Calculation of Defect Parameters in Metals and Alloys, Comparison of Data and Limitations Has Been Reviewed here; Especially Relaxations due to a Vacancy Type of Point Defect, its Formation, Migration, Activation Energies and Related other Parameters Based upon the Present Experimental Status. the Models Reviewed Are the Bond Model, Continuum Model, Semi-Discrete Model, Jellium Model, Thermodynamic Model, Lattice Statics Model, Atomistic Continuum Model and Pseudopotential Model. the Main Thrust Concerns the Last Model. the Taylor, Vashishta and Singwi, Harrison, Kleinmann and King and Kutler Form of Exchange and Correlation Function Are Almost Similar, Give Moderate Results and May Be Trusted for Better Results.

Abstract: A three dimensional phase field model has been developed to simulate the texture formed during the static recrystallisation of FCC metals with medium or high stacking fault energy, such as aluminium, copper and nickel. Before recrystallisation the deformation texture as well as the stored energy was simulated using a three dimensional crystal plasticity finite element model. This output calculated on the distorted finite element mesh was first mapped onto the regular grid of the phase field model using a linear interpolation method and then used as initial condition for the subsequent recrystallisation texture modelling. This model has successfully predicted the typical recrystallisation texture components: cube {001}<100>, R {124}<211> in the aluminium alloy. In addition, the softening fraction and three dimensional microstructure produced during static recrystallisation have also been simulated by this model.

Abstract: For the technology of EBSD, the twinning of metals was described in the form of rotation angle combined with rotation axis, while the twinning of metals was usually described in the form of twinning plane combined with twinning direction. In this report, the corresponding relationship between the two description forms of twinning of face-centered cubic (FCC) metals has been built, based on this relationship, the twinning plane and twinning direction of FCC metals can be determined by EBSD. As the practical application of this relationship above, the twinning variants of two kinds of Ni based superalloys were analyzed.

Abstract: Amplitude dependent internal friction (ADIF) was measured on 4N and 6N Cu crystals at 4K–40 K to study the interaction between a dislocation and a pinning atom. The temperature dependence of the stress amplitude necessary to produce a constant ADIF was well explained by assuming the Cottrell type interaction potential based on linear elasticity. This is clearly different from the case of Al crystals where it was necessary to consider a modified Cottrell potential including a deviation from linear elasticity near the dislocation center.

Abstract: In fast diffusion, the impurity diffusion coefficient is much greater than the self-diffusion coefficient. The pair mechanism is here considered to explain fast diffusion. Formulations for the formation of the pair are based upon pseudopotential theory.

Abstract: Graphs of monovacancy formation energy ( ) versus the parameter, , of Ashcroft's empty-core model potential (AECMP) and nine different exchange and correlation functions (ECF) are shown for two different group-IIa divalent fcc metals (Ca and Sr) and seven group-VIII divalent fcc metals in an active valence state (γ-Fe, β-Co, Rh, Ir, Ni, Pd and Pt). The criterion used is that is greater than the Bohr radius. There is a systematic increase and decrease in the fitted value of , and the calculated value of , respectively, in going from one ECF to other, as follows: Sham

11