Papers by Author: Juan Daniel Muñoz-Andrade

Abstract: The essential objective of this work is to establish the influence of grain size and thermo-mechanical conditions on the activation energy for super plastic flow (Q_SPF) in Ti-6Al-4V alloy by applying the quantum mechanics and relativistic model (QM-RM) proposed by Muñoz-Andrade, in the framework of the unified physics. The QM-RM allows the direct determination of the Q_SPF in advanced materials at instantaneous thermo-mechanical material working conditions. By applying, the QM-RM on the experimental results reported previously by some authors, it is shown for grain size of 6.1μm, that the calculated Q_SPF for grain boundary sliding is about 193 and 178 kJ/mol, at 850°C with an efficiency of power dissipation, η=0.65. These results are in closed agreement with the values of 204 and 174 kJ/mol reported previously for grain boundary self-diffusion energy of α-Ti. Nevertheless, for grain size of 0.6μm the calculated Q_SPF is 142 kJ/mol at 650°C, with an efficiency of power dissipation, η=0.61. As well, in order to understand the phenomenology and mechanics of SPF in Ti-6Al-4V alloy, the variation of the activation energy with the temperature; stress and strain rate is analyzed in association with coupled mechanisms during SPF, such as grain boundary sliding, cooperative grain boundary sliding and self-accommodation process related to the microstructure. In summary, the results of Q_SPF obtained in this work, by the QM-RM are in closed agreement with results reported previously by using the theoretical and conventional methodology set up by Mohamed and Langdon.

Abstract: In the framework connected with the unification of physics, the activation energy for super plastic flow in advanced materials has been obtained by applying the new quantum mechanics and relativistic model proposed by Muñoz-Andrade. This new model allows the direct evaluation of the activation energy for super plastic flow at instantaneous thermo-mechanical material forming conditions. Also, in order to establish the phenomenology and mechanics of super plastic flow, the dependence on strain rate and phase velocity de Broglie is obtained, for the reason that the nature wavelength of the cellular dislocations is essential in the association with coupled mechanisms during super plastic flow, such as grain boundary sliding, cooperative grain boundary sliding and self-accommodation process. In conclusion, cellular dislocation dynamics is a nature mechanism during super plastic flow in advanced materials. The results obtained in this work are in a closed agreement with results reported previously.

Abstract: Microstructural evolution during in situ tension test at constant crosshead velocity of 0.38 mm/min, at room temperature of polycrystalline Pb-50%Sn alloy are reported. Direct observation during four steps of deformation, with a total deformation (ε_T) of 0.684, allows establish that the trajectories of grains during irreversible deformation process obey a sigmoidal motion. Such behaviour is related with dynamic recrystallization phenomenology and associated with grain boundary sliding between neighbouring grains and subsequent cavitation in order to allow emerging grains from the inner volume to free surface of Pb-50%Sn, as the main mechanisms of superplastic flow. The curve of true stress versus true deformation presented several fluctuations during irreversible deformation process in a similar way of the Portevin Le Chatelier effect. Also is observed in the early steps of plastic flow, hardening deformation, up to 27 MPa associated with the maximum stress. The activation energy values for polycrystalline flow, calculated in this work are between 67.5 to 68.07 kJ/mol and there are in a closed agreement with the activation energy of 65.7 kJ/mol, for grain boundary diffusion.

Abstract: ±Abstract. By applying the new quantum mechanics and relativistic mathematical model, proposed by Muñoz-Andrade, on the experimental results reported previously by Aghaie-khafri and Adhami [5], the true activation energy for hot deformation of 15-5 PH stainless steel is obtained over the temperature range of 900-1150°C and strain rates varying between 0.001 and 0.5s-1. It is interesting to contrast the results of this theoretical work with the main results of the apparent activation energy obtained for the same data, but applying the common methodology. It is shown that the true activation energy increased as the hot deformation is increased. Moreover, the true activation energy decreased as the strain rate is increased. The mean value of the true activation energy (289 kJ/mol) at high strain rate, ξ=0.5s-1, for dynamic recrystallization over the temperature range of 900-1150°C is in a closed agreement with the value of activation energy for self-diffusion in γ iron (280 kJ/mol) in dissimilarity of the result of the apparent activation energy (49221 kJ/mol) obtained beforehand by Aghaie-khafri and Adhami [5]. The results obtained in this work by the quantum mechanics and relativistic mathematical model are widely satisfactory; because essentially they are over the crucial limitations of the common methodology to obtain the activation energy at each thermo-mechanical metalworking condition. Keywords: Activation Energy, Hot Deformation, Dynamic Recrystallization, Quantum Mechanics, Special Relativity Theory.

Abstract: The objective of this work is to obtain the mapping of the granular flow during the irreversible deformation processes in spatially extended polycrystalline systems (SEPCS) in order to describe and analyse the phenomenology and mechanics of the granular flow. In general, it was established for commercial alloys that, the granular flow is linked with the hyperbolic motion due to dislocation dynamics and self accommodation of grains. Also, the recession velocity of grains in the stain field on the surface of SEPCS increased with the distance along the tension axis from the origin of the coordinate system of reference. This behaviour is very similar to the Hubble flow associated with the expansion process of the universe, where the recession velocity of the galaxies increased in a linear relationship with their distance. In this physical framework the main results are analysed in the context of the unified interpretation of the Hubble flow, plastic flow and super plastic flow [1-6].

Abstract: The goal of this work is to describe the cosmic micromechanics connection with irreversible deformation processes in spatially extended polycrystalline systems, where the nature of the crystalline structure of the universe in a relativistic framework at Max Plank scale and Edwin Hubble scale play and important role. In this physical construction by applying the theoretical model of Muñoz-Andrade the activation energy for irreversible deformation processes in spatially extended polycrystalline systems is obtained. Consequently, the main results of this work are analyzed in the context of the unified interpretation of Hubble flow, plastic flow and super plastic flow.

Abstract: A unified interpretation of super plastic flow (SPF) and cosmic micromechanics in spatially extended single and polycrystalline systems (SESPS) allows determined that the nature of the hyperbolic granular flow in SESPS is assisted by the movement of dislocations as the pattern of the inner dimension flow. Consequently in this work a mathematical model related with relativistic cosmology and quantum mechanics is used in order to obtain the activation energy for super plastic flow in SESPS. This correspondence law between SPF and cosmic micromechanics is important in the light of recent cosmological theories of the existence of dark matter and dark energy in the cosmic structure, because in this new interpretation of the universe the planets, stars, galaxies, clusters of galaxies, etc., are considered as precipitates on dislocations in the cosmic structure, which is formed in a nature way by the dark matter and dark energy, in a similar form of precipitates on dislocations in a SESPS of metals. Physically in this context the expansion process of the universe is highly dependent upon the volume fraction, size and distribution of precipitates on dislocations in the cosmic structure. Therefore, in this work the main results obtained in cosmic micromechanics and cosmic macromechanics are related with the Max Planck’s scale (MPE) and Edwin Hubble’s scale (EHS) respectively.

Abstract: In connection with ancient and recent view on cosmology, it is interesting to note that our universe could be a spherical crystal and it moves as a crystal in a relative position with others spherical universes, where the Burgers vector for cellular dislocations dynamics is the Hubble length: λH=1.32x1026m. The expansion process of this polycrystalline spatially extended system obey the hyperbolic granular flow, which it is due to an accelerated motion manifested during the deformation process of super plastic advanced structural universes in a similar behaviour of super plastic advanced structural materials. Consequently, in this work the phenomenology and mechanics of super plastic flow are analyzed in the context of the unified interpretation of Hubble flow, plastic flow and super plastic flow, where the combination of fundamentals constants with the natural Planck length, allows obtain in a closed agreement with the Orowan equation the magnitude of the nature Burgers vector of dislocation in the cosmic structure for the universe as follow: 1.62 10 . 35 3 0 x m c H G b P − ⊥ ⊥ ⊥ = = = = h λ ρ ν Where, b⊥ = magnitude of the nature Burgers vector for the universe (b⊥ = 1.62x10-35m), λP = Planck length (λP = 1.62x10-35m), H0 = the Hubble parameter (H0=70 (km/sec)/Mpc = 2.26854593 x10-18s-1), ρ⊥ = dislocation density (ρ⊥ = 1.273x1011 dislocations/m2) in the universe. ν⊥ = the recession velocity of galaxies related with dislocations dynamics in the cosmic structure (ν⊥ = 1100x103 m/s, it is the recession velocity of the Virgo super cluster at 16 Mpc distance). h = h / 2π . Here h = the Planck constant (h = 6.6262x10-34 Joule-s), G = the Newtonian constant (G = 6.67259x10-11 m3/kg s2) and c = the speed of light (c = 299 792 458 m/s) [1-3].

Abstract: Everything in the universe is a result of their own evolution, in consequence all advanced structural materials are physical objects spatially extended in a permanently cosmic connection with the advanced structural universe. In this context, the nature expansion rate of the universe (ξ u) was obtained in a similar way of super plastic flow in terms of the rate reaction theory, with the strong temperature dependence of strain rate as follow: exp 70( / sec)/ 2.26854593 . 18 1 0 − − = =         −         = = km Mpc s kT c Q H P P P u λ ξ Where, QP = the Planck activation energy of the system at the Planck scale (QP = 1.221x1028eV), λP = Planck length (λP = 1.62x10-35m), c = the speed of light (c = 299 792 458 m/s), (c/λP) = the overall frequency factor, k = the Boltzmann constant (k = 8.617x10-5eV/K), TP = the Planck temperature (TP = 1.010285625x1030K) and H0 = the Hubble constant. On the basis of this mathematical expression and their combination with the Orowan equation, it was obtained the mathematical model to predict the activation energy (Q) that is necessary to the glide cellular dislocations during deformation of the super plastic advanced structural materials. Consequently, in this work the application of this mathematical model for super plastic flow in advanced structural materials and the concept of cellular dislocation are reviewed in order to integrate in a general form the unified interpretation of Hubble flow, plastic flow and super plastic flow [1-3].

Abstract: In general, the mechanical behavior of superplastic spatially extended crystalline systems (SP-SECS) is characterized by a sigmoidal relationship between the applied stress and the steady state strain rate. The sigmoidal curve is defined by three regions: low stress - region I, intermediate stress or superplastic - region II and high stress - region III. The region I is known as the region where the threshold stress exists, but there are controversies on their existence. In this way, some experimental results reported in the past are analyzed. Earlier investigations have reported the apparent activation energy for creep in SP-SECS as a function of the applied stress, where it is exhibited a marked dependence of impurities or precipitates concentration. In addition, recent experimental evidences have revealed that the unified interpretation of creep, plasticity and superplasticity is the deductive rule [1]. In order to describe the interaction between precipitates at grain boundaries and dislocations during deformation processes a phenomenological expression for the threshold stress at the Grain Boundary in SP-SECS is described in this work.