Effect of grain size on tensile behaviour of a submicron grained Al–3 wt-%Mg alloy produced by severe deformation

Preface. Introduction. I: Innovations in Severe Plastic Deformation Processing and Process Modeling. Severe Plastic Deformation of Materials by Equal Channel Angular Extrusion (ECAE) R.E. Goforth, et al. Severe Plastic Deformation of Steels: Structure, Properties and Techniques S.V. Dobatkin. Application of ECAP - Technology for Producing Nano- and Microcrystalline Materials V.I. Kopylov. Severe Deformation Based Process for Grain Subdivision and Resulting Microstructures A.K. Ghosh, W. Huang. Modeling of Continual Flows in Angular Domains B.V. Koutcheryaev. Synthesis and Characterization of Nanocrystalline Tial Based Alloys O.N. Senkov, F.H. Froes. Formation of Submicrocrystalline Structure in TiAl and Ti3Al Intermetallics via Hot Working G. Salishchev, et al. Severe Plastic Deformation Processes Modeling and Workability S.L. Semiatin, et al. The Effect of Strain Path on the Rate of Formation of High Angle Grain Boundaries During ECAE P.B. Prangnell, et al. Thermomechanical Conditions for Submicrocrystalline Structure Formation by Severe Plastic Deformation F.Z. Utyashev, et al. II: Microstructural Characterization and Modeling of Severe Plastic Deformation Materials. Strengthening Processes of Metals by Severe Plastic Deformation. Analyses with Electron and Synchrotron Radiation M.J. Zehetbauer. Size Distribution of Grains or Subgrains, Dislocation Density and Dislocation Character by Using the Dislocation Model of Strain Anisotropy in X-Ray Line Profile Analysis T. Ungar. X Ray-Studies and Computer Simulation of Nanostructured SPD Metals I.V. Alexandrov. An Analysis of Heterophase Structures of Ti3Al, TiAl, Ni3Al Intermetallics Synthesized by the Method of the SphericalShock Wave Action B.A. Greenberg, et al. Structural Changes Induced by Severe Plastic Deformation of Fe- and Co-Based Amorphous Alloys N. Noskova, et al. Structure of Grains and Internal Stress Fields in Ultrafine Grained NI Produced by Severe Plastic Deformation N.A. Koneva, et al. Crystal Lattice Distorsions in Ultrafine-Grained Metals Produced by Severe Plastic Deformation A.N. Tyumentsev, et al. Grain and Subgrain Size-Distribution and Dislocation Densities in Severely Deformed Copper Determined by a New Procedure of X-Ray Line Profile Analysis T. Ungar, et al. Calculation of Energy Intensity and Temperature of Mechanoactivation Process in Planetary Ball Mill by Computer Simulation E.V. Shelekhov, et al. III: Microstructure Evolution During Severe Plastic Deformation Processing. Microstructural Evolution During Processing by Severe Plastic Deformation T.G. Langdon, et al. Characterization of Ultrafine-Grained Structures Produced by Severe Plastic Deformation Z. Horita, et al. Fragmentation in Large Strain Cold Rolled Aluminium as Observed by Synchrotron X-Ray Bragg Peak Profile Analysis (SXPA), Electron Back Scatter Patterning (EBSP) and Transmission Electron Microscopy (TEM) E. Schafler, et al. Influence of Thermal Treatment and Cyclic Plastic Deformation on the Defect Structure in Ultrafine-Grained Nickel E. Thiele, et al. Nanostructure State as Nonequilibrium Transition in Grain Boundary Defects in SPD Condition O.B. Naimark. Texture, Structural Evolution and Mechanical Properties in AA5083 Processed by ECAE L. Dupuy, et al. A TEM-Based Disclination Model for the Substructure Evolution under Severe Plastic Deformation M. Seefeldt, et al. Physical Mesomechanics of Ultrafine-Grained Metals V.E. Panin. Microstructure Evo

In debris flow modelling, the viscosity and yield stress of fine-grained sediments should be determined in order to better characterize sediment flow. In particular, it is important to understand the effect of grain size on the rheology of fine-grained sediments associated with yielding. When looking at the relationship between shear stress and shear rate before yielding, a high-viscosity zone (called pseudo-Newtonian viscosity) towards the apparent yield stress exists. After yielding, plastic viscosity (called Bingham viscosity) governs the flow. To examine the effect of grain size on the rheological characteristics of fine-grained sediments, clay-rich materials (from the Adriatic Sea, Italy; Cambridge Fjord, Canada; and the Mediterranean Sea, Spain), silt-rich debris flow materials (from La Valette, France) and silt-rich materials (iron tailings from Canada) were compared. Rheological characteristics were examined using a modified Bingham model. The materials examined, including the Canadian inorganic and sensitive clays, exhibit typical shear thinning behavior and strong thixotropy. In the relationships between the liquidity index and rheological values (viscosity and apparent yield stress), the effect of grain size on viscosity and yield stress is significant at a given liquidity index. The viscosity and yield stress of debris flow materials are higher than those of low-activity clays at the same liquid state. However the viscosity and yield stress of the tailings, which are mainly composed of silt-sized particles, are slightly lower than those of low-activity clays.

Microstructure and mechanical properties of 5056 Al alloy processed by equal channel angular extrusion

Effect of grain size and free interstitials on yield stress, flow stress and Lüders strain in iron and an iron-titanium alloy

The mechanics of equal channel angular extrusion (ECAE) in a rectangular die was studied by upper bound method and rigid block model of deformation with two variables (two degrees of freedom). The appearance of a dead zone in the die external corner was assumed and verified by physical simulation using plasticine as a modeling material. The obtained dependences of ECAE pressure, total ECAE shear and geometrical parameters of dead zone upon friction factor were compared with corresponding results of upper bound rigid block analysis with one variable (one degree of freedom) and with the results of slip line analysis published by the authors elsewhere. It was demonstrated that an increase in degrees of freedom in an ECAE rigid block model from one to two results in much better approximation of the reference data of slip line analysis. The authors believe that an increase in the numbers of degrees of freedom and flexibility of a rigid block model generally leads to a better accuracy in modeling of other metal forming processes as well. As an example, the ECAE pressure of the aluminum 6061 alloy was calculated and compared with the experimental data from literature. A good agreement between them was found. The importance of consideration of friction in the inlet and outlet die channels was emphasized.

Using equal channel angular extrusion (ECAE) process, which combine the advantages of grain refinement and induced strain, for preparing semisolid billets is a relatively new Strain Induced Melt Activation(SIMA)method. This paper investigates the remelting and semisolid isothermal holding behavior of Mg-9Al alloy after ECAE processing at 350°C. It has been found that 2 passes ECAE-ed billets are qualified for obtaining spherical grains after remelting and isothermal holding treatment. Increasing the ECAE process from 2 passes to 8 passes has no further significant effects on the size and roundness of the solid particles at the semisolid state. The effects of temperature and isothermal holding time on microstructural evolution have also been investigated. In addition, the solid solution treatment before the ECAE processing affected greatly on microstructural evolution of the alloy during ECAE processing and thus the following remelting and isothermal holding behavior. The Mg17Al12 precipitates were uniformly decomposed from the saturated solid solution in the solutionized samples during ECAE processing. The coalescence of grains together with the self-blocking effect generated more entrapped liquid in the solutionized sample at semisolid state. Moreover, the solid particles of solutionized samples have bigger size and grow faster, which are detrimental to SSM processability.

The shear plastic deformation behavior of a material during equal channel angular (ECA) extrusion is governed primarily by the die geometry, the material properties, and the processing conditions. Using commercial DEFORMTM 2D rigid-plastic finite element code, this study investigates the plastic deformation behavior of Ti-6Al-4V titanium alloy during 1- and 2-turn ECA extrusion processing in dies containing right-angle turns. The simulations investigate the distributions of the billet mesh, effective stress and effective strain under various processing conditions. The respective influences of the channel curvatures in the inner and outer regions of the channel corner are systematically examined. The numerical results provide valuable insights into the shear plastic deformation behavior of Ti-6Al-4V titanium alloy during ECA extrusion.

The effect of grain size and deformation sub-structure on mechanical properties of polycrystalline aluminum

Low-temperature compaction of Ti–6Al–4V powder using equal channel angular extrusion with back pressure

Effect of MgO addition and grain size on the electrical properties of Ce0.9Gd0.1O1.95 electrolyte for IT-SOFCs

The shear plastic deformation behavior of a material during equal channel angular (ECA) extrusion is governed primarily by the die geometry, the material properties, and the process conditions. This paper employs the rigid-plastic finite element (FE) to investigate the plastic deformation behavior of Ti-6Al-4V titanium alloy during ECA extrusion processing. Under various ECA extrusion conditions, the FE analysis investigates the damage factor distribution, the effective stress-strain distribution, and the die load at the exit. The relative influences of the internal angle between the two die channels, the friction factors, the titanium alloy temperature and the strain rate of billet are systematically examined. In addition, the Taguchi method is employed to optimize the ECA process parameters. The simulation results confirm the effectiveness of this robust design methodology in optimizing the ECA processing of the current Ti-6Al-4V titanium alloy.

We examined applicability of equal channel angular extrusion (ECAE) to improvement of plastic deformability of glassy polymers. Polycarbonate (PC) and poly(methyl methacrylate) (PMMA) were extruded at various temperatures ranging from 50°C to just below the glass transition temperature through one of three equal channel angular dies (ECA-dies) having a pass angle 2φ of 90°, 120° and 150°. Both PC and PMMA could successfully be extruded at most of all conditions examined in this study, although PMMA could not be extrudable at temperatures below about 60°C. After processed through ECAE, extruded PC and PMMA were subjected to tensile test. It was found that ECAE lessened the tensile yield stress of the glassy polymers when extrusion was performed at a lower temperature and through an ECA-die with a larger pass angle 2φ. Plastic flow stress did not so much increase in polymers extruded through an ECA-die with a larger 2φ. Thus, ECAE at a lower temperature through a die with a larger pass angle 2φ was found to be effective to improve plastic deformability of glassy polymers.

Investigation of microstructure characteristics of commercially pure aluminum during equal channel angular extrusion

Equal channel angular extrusion (ECAE) was applied to an as-cast AZ91D magnesium alloy. The strain amplitude dependence and temperature dependence of damping capacities of the as-cast and ECAE processed AZ91D alloys were investigated by dynamic mechanical analyzer (DMA). Microstructures of AZ91D alloys after ECAE were observed by optical microscopy (OM). In higher strain region, the damping value of 4-pass ECAE deformed AZ91D alloy was the highest among all the AZ91D alloys under different conditions. The damping peaks of ECAE deformed AZ91D alloys detected during heating from room temperature to 400°C were considered to be related to the migration of grain boundaries and the movement of dislocations during recrystallization.

Various methods for the production of bulk nanostructured (NS)/ultrafine-grained (UFG) materials have been developed, including equal channel angular extrusion (ECAE), a form of severe plastic deformation. Using an ECAE NS/UFG copper bar as an example, this study has investigated machining-induced workpiece microstructure variation using X-ray diffraction. It has been found that (1) under gentle cutting conditions, there was a 10% increase in the median grain size compared with unmachined ECAE NS/UFG copper bars. Increases in the arithmetic-, area-, and volume-weighted grain sizes were found to be 10%, 8%, and 8%, respectively, and (2) an average 27% drop in the dislocation density was observed between the machined and unmachined ECAE copper bars. The dislocation density was shown to have the most reduction (−39%) at the outer radius of the machined ECAE bar where more heat and/or higher pressure were experienced.