Stored Energy and Annealing Behavior of Heavily Deformed Aluminium

2012 ◽  
Vol 715-716 ◽  
pp. 367-372 ◽  
Author(s):  
Naoya Kamikawa ◽  
Xiao Xu Huang ◽  
Yuka Kondo ◽  
Tadashi Furuhara ◽  
Niels Hansen
Keyword(s):  
Structural Parameters ◽  
Boundary Energy ◽  
Annealing Treatment ◽  
Stored Energy ◽  
Annealing Behavior ◽  
Roll Bonding ◽  
Boundary Spacing ◽  
Long Time ◽  
One Step ◽  
Relative Change

t has been demonstrated in previous work that a two-step annealing treatment, including a low-temperature, long-time annealing and a subsequent high-temperature annealing, is a promising route to control the microstructure of a heavily deformed metal. In the present study, structural parameters are quantified such as boundary spacing, misorientation angle and dislocation density for 99.99% aluminium deformed by accumulative roll-bonding to a strain of 4.8. Two different annealing processes have been applied; (i) one-step annealing for 0.5 h at 100-400°C and (ii) two-step annealing for 6 h at 175°C followed by 0.5 h annealing at 200-600°C, where the former treatment leads to discontinuous recrystallization and the latter to uniform structural coarsening. This behavior has been analyzed in terms of the relative change during annealing of energy stored as elastic energy in the dislocation structure and as boundary energy in the high-angle boundaries.

The Role of Deformation Microstructure in Recovery and Recrystallization of Heavily Strained Metals

2012 ◽  
Vol 715-716 ◽  
pp. 251-258 ◽  
Author(s):  
Niels Hansen
Keyword(s):  
High Strain ◽  
Equal Channel Angular Extrusion ◽  
High Pressure Torsion ◽  
Large Fraction ◽  
Boundary Energy ◽  
Local Scale ◽  
Stored Energy ◽  
High Angle ◽  
Roll Bonding

Metals deformed to high and ultrahigh strains are characterized by a nanoscale microstructure, a large fraction of high angle boundaries and a high dislocation density. Another characteristic of such a microstructure is a large stored energy that combines elastic energy due to dislocations and boundary energy. Parameters of the deformed microstructure significantly affect annealing processes such as recovery and recrystallization. For example, the recovery rate can be significantly increased after high strain deformation and restoration may occur as either discontinuous recrystallization or structural coarsening. A characterization and analysis of deformed and annealed microstructures presented in this work covers Al, Ni, Cu and Fe heavily deformed by rolling, accumulative roll bonding (ARB), equal channel angular extrusion (ECAE) and high pressure torsion (HPT). The important effect of recovery on subsequent restoration processes is discussed along with the effect of heterogeneities both on the local scale and on the sample scale.

Generalized Vertex Model - Study of Recrystallization in Copper

2007 ◽  
Vol 558-559 ◽  
pp. 1157-1162 ◽  
Author(s):  
Krystian Piękoś ◽  
Jacek Tarasiuk ◽  
Krzysztof Wierzbanowski ◽  
Brigitte Bacroix
Keyword(s):  
Grain Boundary ◽  
Texture Evolution ◽  
Boundary Energy ◽  
Annealing Treatment ◽  
Energy Difference ◽  
Primary Recrystallization ◽  
Recrystallization Process ◽  
Vertex Model ◽  
Stored Energy ◽  
Boundary Misorientation

Classical vertex model till now described only the grain growth stage and not the primary recrystallization. In the present work the vertex model is first extended in order to take into account the both stages of recrystallization process. The influence of the stored energy is taken into account and some phenomenological laws describing the evolution of grain boundary energy and mobility with misorientation angle are used. Nucleation is considered to be site-saturated. The experimentally determined stored energy values, crystallographic orientations and boundary misorientation distributions are used in order to characterize the initial microstructure. The model is tested to study the recrystallization of 70% and 90% cold rolled polycrystalline copper during an annealing treatment. In order to explain the texture evolution in both cases, it is necessary to introduce an energy threshold for grain boundary movement, i.e. a minimal value of the stored energy difference between a nucleus and the deformed material necessary to provoke grain boundary motion. The developed model is shown to predict texture evolutions in good agreement with experimental data.

Evaluation of stored energy after accumulative roll bonding of an interstitial-free steel by means of orientation microscopy data

2005 ◽  
Vol 38 (4) ◽  
pp. 668-674 ◽  
Author(s):  
K. Lee ◽  
A. C. C. Reis ◽  
G. Kim ◽  
L. Kestens
Keyword(s):  
Accumulative Roll Bonding ◽  
Cellular Network ◽  
Boundary Energy ◽  
Orientation Imaging Microscopy ◽  
Radius Of Curvature ◽  
Interstitial Free ◽  
Stored Energy ◽  
Roll Bonding ◽  
Local Boundary ◽  
Von Mises

The stored energy of warm-rolled interstitial-free steels, produced in an accumulative roll bonding process, is evaluated by using the textural and microstructural information contained in orientation imaging microscopy (OIM) scans which were measured after accumulated von Mises strains (∊vM) of 0.8, 1.6, 2.4 and 4.0, respectively. It is assumed that the plastic strain energy is stored in a cellular network of local boundaries of low and high misorientations. The presence of intracellular dislocations which do not contribute to a local crystal orientation gradient is ignored in the present analysis. On the basis of the Read–Shockley equation, the local misorientation can be associated with a local boundary energy which can be expressed as a local stored energy by taking into account the radius of curvature of the cellular network. The validity of this procedure was verified by comparing the integrated average stored energy of the sample with the Vickers hardness data, which produced a reasonable correspondence. The present analysis also allowed the calculation of the stored energy distribution in the areas of the orientation representation space which were sufficiently populated by sample crystal orientations,i.e.the γ fibre (〈111〉||ND) of the present deformation texture. The distribution of stored energy along this fibre displayed a maximum on the {111}〈211〉 texture component, particularly after a von Mises strain of 1.6, whereas the {111}〈110〉 component displayed a local minimum of stored energy after ∊vM= 2.4 and 4.0.

The Emergence of Bone Technologies at the End of the Pleistocene in Southeast Asia: Regional and Evolutionary Implications

2012 ◽  
Vol 22 (1) ◽  
pp. 37-56 ◽  
Author(s):  
Ryan J. Rabett ◽  
Philip J. Piper
Keyword(s):  
Early Modern ◽  
Large Scale ◽  
Minor Component ◽  
Modern Human ◽  
Small Element ◽  
Adaptive Process ◽  
Long Time ◽  
One Step ◽  
A Minor

For many decades Palaeolithic research viewed the development of early modern human behaviour as largely one of progress down a path towards the ‘modernity’ of the present. The European Palaeolithic sequence — the most extensively studied — was for a long time the yard-stick against which records from other regions were judged. Recent work undertaken in Africa and increasingly Asia, however, now suggests that the European evidence may tell a story that is more parochial and less universal than previously thought. While tracking developments at the large scale (the grand narrative) remains important, there is growing appreciation that to achieve a comprehensive understanding of human behavioural evolution requires an archaeologically regional perspective to balance this.One of the apparent markers of human modernity that has been sought in the global Palaeolithic record, prompted by finds in the European sequence, is innovation in bonebased technologies. As one step in the process of re-evaluating and contextualizing such innovations, in this article we explore the role of prehistoric bone technologies within the Southeast Asian sequence, where they have at least comparable antiquity to Europe and other parts of Asia. We observe a shift in the technological usage of bone — from a minor component to a medium of choice — during the second half of the Last Termination and into the Holocene. We suggest that this is consistent with it becoming a focus of the kinds of inventive behaviour demanded of foraging communities as they adapted to the far-reaching environmental and demographic changes that were reshaping this region at that time. This record represents one small element of a much wider, much longerterm adaptive process, which we would argue is not confined to the earliest instances of a particular technology or behaviour, but which forms part of an on-going story of our behavioural evolution.

Cross-Sectional Texture Gradients in Interstitial Free Steels Processed by Accumulated Roll Bonding

2005 ◽  
Vol 105 ◽  
pp. 233-238 ◽  
Author(s):  
Ana Carmen C. Reis ◽  
Leo Kestens
Keyword(s):  
Plane Strain ◽  
True Strain ◽  
Orientation Imaging Microscopy ◽  
Lamellar Microstructure ◽  
Annealing Treatment ◽  
Rolled Sheet ◽  
Interstitial Free ◽  
Cross Sectional ◽  
Roll Bonding ◽  
Significant Difference

An interstitial-free steel was severely plastically deformed in an accumulative roll bonding (ARB) experiment with 10 consecutive passes applied at 480°C. Nominal reductions of 50% per pass and an intermediate annealing treatment of 5 min. at 520°C were employed. A total true strain of evM = 8.00 was applied, which corresponds to an accumulated reduction of 99.9%. The evolution of texture and microstructure was monitored by means of orientation imaging microscopy. A lamellar microstructure, characteristic of severely rolled sheet materials, was observed even after the highest strains. The average lamellar width was determined as a function of rolling strain. Under the experimental limitations in terms of spatial resolution, no significant difference was observed between the average lamellar width in the mid-section and near the surface of the sheet. Texture analysis revealed a conventional cross-sectional gradient with plane strain rolling components in the mid-layers and shear components in the subsurface regions. Although these different strain modes did not affect the microstructure in terms of the average lamellar spacing, an effect was observed on the average aspect ratio of the grains. This was much higher in the sheared (surface) layers than in the plane strain compressed (centre) areas. The surface structure did not have an effect, though, on the bulk microstructural evolution in spite of the specific nature of the ARB process during which the surface layer of one pass reappears in the mid-section of the next pass.

scholarly journals Interfacial Bonding Mechanism Ofaluminium and Steel Composites

2018 ◽  
Vol 27 (2) ◽  
pp. 096369351802700 ◽  
Author(s):  
Xian Yang ◽  
Hao Weng ◽  
Chao-lan Tang
Keyword(s):  
Bonding Strength ◽  
Annealing Treatment ◽  
Physical Contact ◽  
Diffusion Annealing ◽  
Al Alloy ◽  
Bonding Mechanism ◽  
Chemical Action ◽  
Roll Bonding ◽  
Two Component ◽  
Metallic Bonding

The research on singular material is gradually converted to composite material which serves to rectify weaknesses possessed by each constituent when it exists alone. Experiments on Al-alloy 4A60 and 08Al steel plate compounded by cold roll bonding were conducted to analyze the bonding mechanism of the interface during the composite process of laminated metal. SEM, EDS, and laser confocal microscope were used to observe the interface and section of composites while the bonding strength was tested by universal tensile machine. The result showed that bonded metal's surface microtopography, reduction and diffusion annealing were the most critical influences on the bonding of composites, and the roll bonding mechanism of 4A60/08Al composite was divided into three stages: 1) Physical contact. Two component layers were mechanically occluded by the rolling pressure, the bonding strength was low; 2) Metallic bonding. The oxide layer and the hardened layer covered on the metal surface break which made the two component fresh metals to full contact, chemical action happened and metallic bonding formed when the interatomic distance reached a certain stage, the bonding strength increased; 3) Metallurgical bonding. In the subsequent annealing treatment, the bonding strength significantly increased because the diffusion of metal atoms at the interface.

Use of Stored Energy Distribution in Stochastic Vertex Model

2008 ◽  
Vol 571-572 ◽  
pp. 231-236 ◽  
Author(s):  
Krystian Piękoś ◽  
Jacek Tarasiuk ◽  
Krzysztof Wierzbanowski ◽  
Brigitte Bacroix
Keyword(s):  
Energy Distribution ◽  
Boundary Energy ◽  
Monte Carlo Algorithm ◽  
Recrystallization Process ◽  
Polycrystalline Copper ◽  
Vertex Model ◽  
Stored Energy ◽  
Random Modification ◽  
Important Input ◽  
Versus Crystal

The stored energy distribution versus crystal orientation in polycrystalline copper was determined using synchrotron radiation. This distribution is an important input data for recrystallization models. The stochastic vertex model of recrystallization was used in the present work. It is a mixture of the classical vertex model and the Monte Carlo algorithm. Both grain boundary energy and stored energy are taken into account in the calculations. In each elementary step, a reasonably small, random modification of a given vertex position is generated and a corresponding total energy change of a system is calculated. A new vertex position is retained with a probability proportional to the Boltzmann factor. In such a way one avoids solving a complex system of equations. This approach is also closer to the stochastic nature of recrystallization process. The inclusion of the stored energy distribution in the above model enables a good explanation of the recrystallization process. The recrystallization textures for polycrystalline copper rolled to low and high reductions were predicted in agreement with experimental results.

Synthesis of Hollow and Hierarchical NiO Nanosheets Nanotubes and their Application as Supercapacitor Electrodes

2013 ◽  
Vol 467 ◽  
pp. 215-220
Author(s):  
Xin Xu ◽  
Shu Jiang Ding ◽  
De Mei Yu
Keyword(s):  
Chemical Composition ◽  
Electrochemical Performance ◽  
Annealing Treatment ◽  
Core Shell ◽  
Tubular Structures ◽  
Shell Nanostructures ◽  
Hollow Interior ◽  
One Step ◽  
Thermal Annealing Treatment ◽  
Nio Nanosheets

Hollow and hierarchical NiO nanosheets nanotubes were successfully prepared through a one-step solvothermal route followed by a thermal annealing treatment. The microstructure and chemical composition of Ni-precursor@PNT core-shell nanostructures and calcined NiO nanosheets nanotubes are investigated by SEM, TEM, TGA and XRD. The unique NiO nanosheets nanotubes show admirable electrochemical performance as an electrode material for supercapacitors owing to the hierarchically tubular structures and hollow interior.

Simulation of Primary Recrystallization in Automotive Steels by Consideration of Particle Pinning

2007 ◽  
Vol 558-559 ◽  
pp. 171-176
Author(s):  
Shi Hoon Choi ◽  
B.J. Kim ◽  
S.I. Kim ◽  
Jin Won Choi ◽  
Kwang Geun Chin
Keyword(s):  
Grain Boundary ◽  
Fine Particles ◽  
Boundary Energy ◽  
Sheet Steel ◽  
Primary Recrystallization ◽  
Subgrain Structure ◽  
Interstitial Free ◽  
Stored Energy ◽  
Boundary Misorientation ◽  
Grain Boundary Mobility

A modified two dimensional (2-D) Monte Carlo (MC) technique was used to simulate primary recrystallization in automotive steels containing fine particles. In order to consider anisotropic properties of grain boundary energy and grain boundary mobility, functions of boundary misorientation were introduced. Orientation-dependent stored energy developed in 80% cold-rolled interstitial free (IF) sheet steel was evaluated by reconstructing of data measured using electron back-scattered diffraction (EBSD) analysis. A subgrain method based on subgrain structure is used for quantitative analysis of the stored energy. The simulation reveals that particles affect evolution of microstructure during recrystallization. The simulation provided a theoretical foundation for understanding effect of particles on the final microstructures and crystallographic textures.

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