bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Structure on Mechanical and Corrosion Properties of Austenitic Steel Subjected to Neutron Irradiation
Authors: Abramova Marina M. , Alexandrov Igor V. , Shamardin Valentin K. , Bulanova Tatyana M. , Karavaeva Marina V.
Published: December 2010

The initial and deformed states of austenitic stainless steel AISI 321 before and after neutron irradiation with a damage dose up to 5.3 dpa at reactor core temperature of 350 °С were comparatively investigated. Corrosion behavior, mechanical properties are analyzed in the temperature range of 20…650 °С. It is shown that radiation damage of the steel in the deformed state significantly decreases in comparison with the initial coarse-grained state at the same level of corrosion resistance.
Investigation on Corrosion Behaviors of Ultra-Fine Grain Copper in 3.5% NaCl Solution
Authors: Wang Qing Juan , Wang Y.C. , Du Zhong Ze , Liu Xiao Yan
Published: December 2010

The corrosion behavior of ultra-fine grain (UFG) copper bulk prepared by equal channel angular pressing (ECAP) was studied in 3.5% NaCl solution. The effect of ECAP deformation on the copper corrosion is controversial in the literature, and worth to verify by means of various experimental techniques. Corrosion performances of UFG copper were investigated in comparison with that in recrystallized coarse grain (CG) copper by polarization curves, Tafel extrapolation method, electrochemical impedance spectroscopy(EIS). The shape of polarization curves and type of corrosive attack remains the same in the UFG and the coarse-grain state. UFG copper exhibited a lower corrosion current and high self-corrosion potential in comparison with CG copper. Electrochemical experimental results showed that UFG copper increased in resistance to corrosion compared with CG copper. This decrease in corrosion resistance was mainly attributed to the more compact corrosion film of UFG copper. The compact passive film led to decrease of the diffusion capability of ions within the corrosion film and corrosion rate.
Phase Transformations and Super-Elasticity of a Ni-Rich TiNi Alloy with Ultrafine-Grained Structure
Authors: Fan Zhi Guo , Song Jie , Zhang Xiao Ning , Xie Chao Ying
Published: December 2010

A Ni-rich Ti-50.7.at%Ni alloy was processed by Equal Channel Angular Extrusion (ECAE) at 500°C. After 8 passes ECAE, microstructure was refined to sub-micron scale, approximately 0.2 μm～0.3 μm. TEM observation reveals that Ti3Ni4 phase precipitated in Ni-rich Ti-50.7.at%Ni alloy during the preheating treatment before each ECAE pass, but re-dissolved during sequent ECAE processes. After ECAE treatment, the B2R transformation occurred within a larger temperature range. Comparing with the solution-treated TiNi specimen, the martensitic transformations start (Ms) and peak temperatures (Mp) of TiNi specimens ECAEed were dramatically lowered. Super-elasticity characteristics of TiNi alloy were tested by tensile loading and unloading cycles. The results reveal that at a tensile strain of 4% or smaller, ultrafine-grained (UFG) TiNi alloy processed by 4 passes ECAE shows better super-elasticity than solution-treated sample. Microstructure evolution and its effect on phase transformations and super-elasticity characteristics have been discussed.
Status of Commercialization of Nanostructured Metals
Authors: Lowe Terry C.
Published: December 2010

Nanostructured metals hold the potential to significantly augment the product portfolios of the metals industry. This potential is being progressively developed through contributions from the academic community to the underlying science of nanostructuring, increasing development and protection of intellectual property, and the involvement of large corporations. In this paper we review the trends and status of the commercialization of nanostructured metals technology, focusing on metals produced by severe plastic deformation.
Microstructural Features and Mechanical Properties after Industrial Scale ECAP of an Al 6060 Alloy
Authors: Frint Philipp , Hockauf Matthias , Halle T. , Strehl G. , Lampke Thomas , Wagner Martin F.X.
Published: December 2010

Future applications of ultrafine-grained, high performance materials produced by equal-channel angular pressing (ECAP) will most likely require processing on an industrial scale. There is a need for detailed microstructural and mechanical characterisation of large-scale, ECAP-processed billets. In the present study, we examine the microstructure and mechanical properties as a function of location and orientation within large (50 x 50 x 300 mm³) billets of an Al 6060 alloy produced by ECAP (90° channel angle) with different magnitudes of backpressure. The internal deformation is analysed using a grid-line method on split billets. Hardness is recorded in longitudinal and cross-sectional planes. In order to further characterise the local, post-ECAP mechanical properties, tensile tests in different layers are performed. Moreover, low voltage scanning transmission electron microscopy observations highlight relevant microstructural features. We find that the homogeneity and anisotropy of mechanical properties within the billets depend significantly on the geometry of the shear zone. We demonstrate that deformation gradients can be reduced considerably by increasing the backpressure: The opening-angle of the fan-shaped shear zone is reduced from ψ ≈ 20 ° to ψ ≈ 7 ° when the backpressure is increased from 0 to 150 MPa. Backpressures of 150 MPa result in excellent homogeneity, with a relative variation of tensile mechanical properties of less than 7 %. Our investigation demonstrates that ECAP is suitable for processing homogenous, high performance materials on a large scale, paving the way for advanced industrial applications.
Development of SPD Technologies and Establishment of a Production Line for Rod-Shaped Semiproducts out of Nanostructured Titanium for Medical Application
Authors: Raab Georgy I. , Utyashev Farid Z.
Published: December 2010

The paper reports on the investigation results for the criteria required for estimation of the SPD technologies. It has been demonstrated that one of the important criteria is specific surface area of the deformation zone, which enables considering the scale factor during processing and predicting the properties of the processed semi-products and items. Practical use of the results of conducted studies is demonstrated on the example of establishment of a production line for high-strength nanostructured semi-products from CP Ti for medical application.
Interface Microstructure of Diffusion Bonded Fe3Al/Al with Ultrafine Grain Layer
Authors: Ren Jiang Wei , Li Dong , Shan Ai Dang
Published: December 2010

The influence of ultrafine grains produced by severe plastic deformation technology on the weldability of Fe3Al and Al dissimilar materials was investigated. An ultrafine grain layer was produced on Fe3Al intermetallic compound by surface mechanical attrition treatment. Then the SMATed Fe3Al was diffusion bonded with 1060Al at 550°C for 90 min in the vacuum of 10-3 Pa. The microstructures of surface ultrafine grain layer and transition zone at the interface of SMATed-Fe3Al/Al joint were observed by scanning electron microscopy. The grain size of surface ultrafine grains was characterized by X-ray diffractometry. The elements distribution at the interface and the phase constituents of transition zone were measured by energy disperse spectroscopy. The results showed that a deformed layer about 10-20 μm wide and surface nanocrystallines about 35nm were produced after 15 min surface mechanical attrition. SMATed Fe3Al was well bonded with Al and 11-30 µm wide transition zone formed. The transition zone consisted of FeAl and FeAl3 phases. The surface nanocrystallines helped the atom diffusion and the formation of diffusion bonded joint with rough surface and lower pressure.
The Aspects of Practical Application of Ultrafine-Grained Titanium Alloys Produced by Severe Plastic Deformation
Authors: Naydenkin Evgeny V. , Ratochka Il'ya V. , Grabovetskaya Galina P.
Published: December 2010

The mechanical and physical properties of ultrafine-grained titanium alloys produced by severe plastic deformation are considered. It is found that the formation of ultrafine-grained structure in these materials causes a significant enhancement in their mechanical properties at room temperature and in their resistance to hydrogen embrittlement as well as a change in their acoustic properties. Moreover, superplasticity is realized in these materials at less elevated temperatures relative to the respective coarse grained counterparts. It is shown that the above changes in material properties permit optimization of conditions by the production of items from the titanium alloys, e.g. medical implants having the requisite strength and stepped waveguides having long life even in the high power density conditions of an ultrasound system.
Annealing Effect on the Performance of Sputtering Deposited Metglas Thin Films
Authors: Liang Cai , Hu Jing , Prorok Barton C. , Gooneratne Chinthaka , Kosel Jürgen
Published: December 2010

Magnetostrictive sensors based on ferromagnetic materials have been widely used in detecting chemicals and biological species. The MetglasTM 2826MB is one of the bulk strip materials that is employed as the sensor platform. However, the sensitivity is limited by the large size of the sensors itself. In order to improve the sensitivity, we have developed a process to fabricate microscale sensors of 500 x 100 m in size using conventional MEMS technology. As-deposited, the sensors suffered from internal stress, which was released by a annealing the sensors at 215 °C for two hours under vacuum condition. The annealing process improved the magnetic properties of the thin films and increased the resonant frequency of the sensor by 214 kHz.
The Novel Continuous Large Deformation Technology Integrating Conventional Rolling with Equal-Channel Angular Technology
Authors: Zhu X.D. , Xu Xiao Jing , Zhao Z.H. , Chong K. , Cheng C. , Cheng Xiao Nong
Published: December 2010

A new continuous severe plastic deformation (SPD) procedure integrating conventional rolling with equal-channel angular deformation (designated CR-ECA deformation procedure) was investigated. Experimental results show that the SPD procedure has the capacity of realizing continuous SPD processing of long-size work-pieces with good surface qualities. Numerical simulations by using finite element code DEFORM-3D show that the number of roller pairs had significant influences on the the CR-ECA deformation procedure. As the number of roller pairs changed from 1 to 2, 3 and 4, the effective strain increased by 10.1 %, 10.1 % and 16.1 %; the output velocity increased by 10.8 %, 15.9 % and 14.4 %; the torque of the primary feeding roller decreased by 19.0 %, 34.7 % and 45.6 %; the total torque increased by 7.0 %, 11.8 % and 13.4 %; and the energy consumption used for making unit volume work-piece subjected to unit effective straining decreased by 12.2 %, 15.0 % and 19.4 %.
Nanocrystallization and Dissolution of Immiscible Powder Alloys Using High Pressure Torsion
Authors: Kahofer Susi , Zehetbauer Michael J. , Danninger Herbert , Schafler Erhard , Kerber Michael B. , Horky Jelena
Published: December 2010

Precompacts out of immiscible systems CuCr (75/25 wt%) and WCu (80/20 wt%), respectively, were made by pressing mixed powders and sintering. By applying different strains and hydrostatic pressures of HPT at room temperature, disc-shaped samples with a diameter of 8 mm were produced. They were investigated by Light Microscopy, Scanning-Electron Microscopy using Back-Scattered Electrons, and X-ray Line Profile Analysis. In addition, Vickers microhardness data were collected. Both systems showed the highest microhardness at a shear strain of about γ = 170. The density (for the case of Cu25Cr) of the consolidated material could be increased to the theoretical value. Microhardness and grain sizes were studied individually for each of the phases, too.
Effect of Severe Cold-Rolling and Subsequent Annealing on Microstructure and Properties of in-Situ Composite Steel
Authors: Zhao Jun , Zhang Han , Yang Yong Ming , Chen Jiu Chuan , Wen Quan Xing , Wang Zhi , Zhang Li Tao , Gao Yu Wei
Published: December 2010

In this paper, the process of severe cold-rolling and annealing for Q235 steel with lath martensite has demonstrated a new promising technique for producing in-situ composite multi-nanolayer steel. Cold rolling and subsequent annealing have great impact on microstructure evolution as well as mechanical properties. In the as-rolled state, the strength (b 2112 MPa) is approximately four times increased than as-received material, which is attributed to work hardening and grain refining during cold rolling. As cold-rolled sample subjected to further annealing below 500 °C, deformed microstructure underwent further recovery and recrystallization and finally became refined equiaxed grains; ultraﬁne ferrite grains, nano-carbides precipitated uniformly were seen in the specimen annealed at 500 °C, and the phenomenon of fracture delamination was observed from the specimens, the delamination plane was parallel to the rolling plane, in-situ composite weak interfaces effect has great impact on the fracture surface. Annealing at and above 600 °C resulted in coarse ferrite grains with spheroidized coarse carbides, causing grain growth.
Effect of Combined Rolling Processes on Structure and Mechanical Properties of Pure Titanium Rods
Authors: Lopatin Nikolay , Diakonov Grigoriy , Pleshakova Olga
Published: December 2010

This article focuses on the effect of combine rolling processes on structure and mechanical properties of the commercially pure Ti rods. The finite element model had being made. The analysis of strain state at the screw and shape rolling was done. The analysis of microstructure evolution at the warm rolling was completed.
Atomic Scale Investigation of Impurity 3D Distribution in Nanocrystalline Ni Processed by SPD
Authors: Sauvage Xavier , Wilde Gerhard , Valiev Ruslan
Published: December 2010

Some nanocrystaline Ni was prepared by repeated cold rolling with intermediate folding (F&R). The material was then processed by High Pressure Torsion (HPT) to study the grain evolution under additional Severe Plastic Deformation (SPD). Microstructures were characterized by Transmission Electron Microscopy (TEM) and the impurity distribution was analyzed by Atom Probe Tomography (APT). In this paper, we discuss about the influence of impurities on the grain growth during HPT and on the grain size reduction mechanism during SPD.
Nanostructure Formation and Amorphization in Intermetallic Compounds by Severe Plastic Deformation
Authors: Tsuchiya Koichi , Ciuca Octav
Published: December 2010

Process of nanostructure formation and amorphization by high pressure torsion (HPT) were studied for various intermetallic compounds. In ZrCu after HPT deformation, optical microscopy revealed that numerous shear bands formed running nearly parallel to the shear direction. Partial amorphization was confirmed by X-ray diffraction and TEM observations. Detailed TEM observations revealed localized amorphization within the nano-scale shear bands. For HPT deformation of zone-melted Zr50Cu40Al10 the preferential amorphization of ZrCu phase was observed. On the contrary, amorphization was not observed for Ni3Al even after HPT deformation of 100 turns; the sample remained to be disordered nanocrystalline of about 50 nm. The process and mechanism of the grain refinement and amorphization will be compared and discussed for these intermetallic compounds.
Disorientations after Severe Plastic Deformation and their Effect on Work-Hardening
Authors: Pantleon W.
Published: December 2010

Plastic deformation creates orientation differences in grains of originally uniform orientation. These disorientations are caused by a local excess of dislocations having the same sign of the Burgers vector. Their increase with increasing plastic strain is modeled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different types of boundaries are in close agreement with experimental data for small and moderate plastic strains. At large plastic strains after severe plastic deformation, saturation of the measured average disorientation angle is observed. This saturation is explained as an immediate consequence of the restriction of experimentally measured disorientation angles to angles below a certain maximum value imposed by crystalline symmetry. Taking into account the restrictions from crystalline symmetry for modeled disorientation angles does not only lead to an excellent agreement with experimental findings on Ni after high pressure torsion, but also rationalizes the work-hardening behavior at large plastic strains as well as a saturation of the flow stress.
Microstructural Evolution in an Al-6061 Alloy Processed by High-Pressure Torsion and Rapid Annealing
Authors: Loucif Aicha , Figueiredo Roberto B. , Baudin Thierry , Brisset François , Langdon Terence G.
Published: December 2010

The processing of bulk metals through the application of severe plastic deformation provides the opportunity for introducing significant grain refinement into bulk solids. In the present investigation, an aluminum alloy (Al-6061) was processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa up to a total of 5 turns. Detailed measurements after processing revealed the occurrence of continuous grain refinement and material strengthening with increasing imposed strain. The average grain size of the alloy was reduced from ~150 m to a grain size in the range of ~500 nm through processing by HPT. Although there was a difference in the average grain size of samples processed to different levels of imposed strain, careful inspection showed that the structures became similar after annealing at 250°C for 5 min. This suggests that the additional grain refinement introduced at large amounts of deformations is less stable at high temperatures. The results of this investigation, including the distributions of the grain sizes after annealing, are consistent with the predictions of a model based on the occurrence of continuous recrystallization in aluminum alloys having fine grain structures, large fractions of high-angle grain boundaries and where there is a large amount of deformation.
Microstructure and Properties of a Fe-Cu Composite Processed by HPT Powder Consolidation
Authors: Bachmaier Andrea , Pippan Reinhard
Published: December 2010

A method to produce nanocrystalline Fe-Cu composites by means of high-pressure torsion (HPT) deformation is presented. Mixtures of micrometer sized powders of Fe and Cu with different ratios of the two components were precompacted and subsequently deformed by HPT at room temperature to a certain amount of strain. Afterwards, new samples were cut out of these previously deformed samples and further HPT deformation was conducted. The evolution of the microstructure during the different steps of the HPT process and the resulting microstructure of the composites were investigated by scanning electron microscopy. In summary it could be shown that the final attainable grain sizes in the composite materials in the two step process are much smaller than in the simply HPT deformed composites. The reduction of the grain size is also reflected in an enhancement of the hardness.
Quantitative Characterization of Microstructure in Copper Processed by Equal-Channel Angular Pressing
Authors: Král Petr , Dvořák Jiří , Kvapilová Marie , Svoboda Milan , Beneš Viktor , Ponížil Petr , Šedivý Ondřej , Sklenička Václav
Published: December 2010

Experiments were conducted on extremely coarse-grained pure copper to evaluate the effect of equal-channel angular pressing (ECAP) on microstructure evolution in the as-pressed state and after creep exposure using various stereological methods. The microstructure formed by severe plastic deformation is an unusual structure which can be hardly characterized only by the mean grain size especially after low number of ECAP passes. The purpose of this paper is a detailed examination of (sub)boundaries and grain boundaries in the microstructures of the pressed material. The inhomogeneity of deformed microstructures is also evaluated. The detailed description of ECAP microstructures should contribute to the better understanding of mechanical properties of the pressed materials.
Influence of the Precipitation State on Thermal Stability of an Ultra-Fine Grained AlMnFe-Alloy Produced by Equal Channel Angular Pressing
Authors: Berghammer Rolf , Hu Wei Ping , Hasani Arman , Gottstein Günter
Published: December 2010

An aluminum alloy with two different precipitation states was processed by Equal Channel Angular Pressing up to 16 passes. The thermal stability of the ultra-fine grain structure was examined during annealing at 300°C up to 1 h. As the present precipitates are coarse they don’t contribute to strengthening where as soluted elements improved the strength of the material. Additionally the soluted elements formed dispersoids upon annealing and thereby retarded softening.
Structural Evolution on the Cross-Section of an AZ31 Magnesium Alloy Processed by High-Pressure Torsion
Authors: Figueiredo Roberto B. , Langdon Terence G.
Published: December 2010

Disks of an AZ31 magnesium alloy were processed by High-Pressure Torsion (HPT) at 463 K to different numbers of rotations. The grain structure was evaluated along the cross-section of the disks using optical microscopy. Significant heterogeneities in the average grain size were observed in areas of the disks which were located at similar distances to the center but at different distances from the surface. Moreover, different grain structures were observed in neighboring areas and shear bands occurred at several locations in the disks. Microhardness tests revealed differences in the strength of the material as a function of the distance to the surface. An analysis of the grain structure and hardness distribution suggests the occurrence of flow localization in HPT processing.
Aging Behavior of Al-Mg-Si Alloys Processed by High-Pressure Torsion
Authors: Akama Daichi , Horita Z. , Matsuda Kenji , Shoichi Hirosawa
Published: December 2010

This research investigates simultaneous strengthening by grain refinement and fine precipitation in age-hardenable Al-Mg-Si alloys containing an additional element of either Ag, Cu, Pt or Pd. The alloys were solution-treated and processed by high-pressure torsion (HPT) at room temperature under a pressure of 6 GPa. They were aged at a temperature of 373 K for up to a total period of 6.7 hours. Vickers microhardness was measured after selected periods of aging and the microstructures were observed by transmission electron microscopy. It was found that, in all alloys, the grain sizes after HPT were refined to 300-400 nm and there were significant increases in the hardness through the HPT processing. The hardness was further increased by the subsequent ageing treatment, confirming the simultaneous strengthening by grain refinement and fine precipitation. However, the aging behavior was different depending on the alloying compositions.
The Evolution of Homogeneity during Processing of Aluminium Alloys by HPT
Authors: Alhajeri Saleh N. , Kawasaki Megumi , Gao Nong , Langdon Terence G.
Published: December 2010

Disks of a commercial purity aluminium Al-1050 alloy and Al-1%Mg alloy were processed by high-pressure torsion (HPT) at room temperature for up to a maximum of 5 turns under a pressure of 6 GPa. Following processing, hardness measurements were recorded across the surfaces of the disks. These measurements showed low values of hardness at the center and high values near the edges of the disks and the hardness increased in both alloys with increasing numbers of turns. The evolution of homogeneity in hardness was rapid in Al-1050 compared to the Al-1%Mg alloy. After 5 turns of HPT under a pressure of 6 GPa, the hardness was fully homogeneous across the total surface of the Al-1050 disk whereas there was a region of lower hardness around the center of the Al-1%Mg disk. The results reveal the significant difference between both alloys where the higher rate of recovery in the Al-1050 alloy leads to a rapid evolution of the hardness homogeneity.
Effect of Cold Rolling on Structure and Mechanical Properties of Copper Subjected to Different Numbers of Passes of ECAP
Authors: Stepanov Nikita , Kuznetsov A.V. , Salishchev Gennady A. , Raab Georgy I. , Valiev Ruslan
Published: December 2010

Commercial purity copper was subjected to ECAP and subsequent cold rolling. Structure and mechanical properties were studied using EBSD analysis, TEM and tensile tests. Effect of ECAP number passes on grain size and fraction of high angle boundaries after cold rolling was investigated. Rolling results in grain refinement and HABs fraction increase the more ECAP number passes. UTS increases significantly after rolling. Increase of strength is accompanied by loss of plasticity. Evolution of microstructure and mechanical properties is discussed.
Major Landmarks of NanoSPD Activity: International Conferences from NanoSPD1 to NanoSPD5
Authors: Valiev Ruslan
Published: December 2010

Nanjing University is hosting the 5-th in a row of NanoSPD conferences, which continues a series of the preceding conferences: in Moscow (1999), Vienna (2002), Fukuoka (2005) and Goslar (2008). This paper highlights the major landmarks of NanoSPD activity for the past years from the standpoint of the International NanoSPD Steering Committee. Special attention is given to topics relating to nanostructuring of metals by SPD processing for advanced properties as well as new trends in developing SPD techniques for practical application. Another concern of the committee is in introduction and discussion of the terminology applied in this new field of science and engineering.
Aging Behavior of Cu-Ni-Si Alloy Processed by High-Pressure Torsion
Authors: Matsunaga Hirotaka , Horita Z. , Imamura Kazutaka , Kiss Takanobu , Sauvage Xavier
Published: December 2010

An age-hardenable Cu-2.9%Ni-0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ~150 nm and the Vickers microhardness was significantly increased through the HPT process. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis revealed that fine precipitates with sizes of ~20 nm or smaller were formed in the Cu matrix and some particles consist of Ni and Si with no appreciable amount of Cu.
A Study on Characteristics of Microstructures and Orientations of UFG Materials Prepared by SPD
Authors: Shi Qing Nan , Chen Yong Jin , Wang Jun Li
Published: December 2010

In the paper, the study was conducted on the characteristics of microstructures and orientations of UFG pure copper and 6061 aluminum alloy prepared by AARB, ECAP and CECC severe plastic deformation processes, in which SEM, TEM, EBSD and X-ray diffraction techniques were employed. The result of the study shows that microstructures, mainly composed of subgrains and dislocation kinks, are profuse in the UFG materials by the three SPDs. These kinds of microstructures have the strength of the materials much enhanced and the toughness heavily decreased. In these processes, shear deformation makes gains get finer and finer with the existence of the preferred orientations in the prepared UFG materials. Nevertheless, CECC shows the heaviest effect on the grain refining and the preferred orientation weakening.
Recrystallization Mechanisms Leading to the Formation of Nanoscale Grains in a Ni-20%Cr Alloy Subjected to Intense Plastic Deformation
Authors: Dudova Nadezhda , Belyakov Andrey , Kaibyshev Rustam
Published: December 2010

Microstructure evolution during annealing of a Ni-20%Cr alloy subjected to high-pressure torsion (HPT) at ambient temperature was examined. It was shown that recrystallization processes are dependent on the annealing temperature and strain. Discontinuous static recrystallization (DSRX) took place in the alloy strained to <3. Continuous grain growth (GG) occured under subsequent annealing in the material strained to ≥6. It was attributed to the fact that HPT led to the formation of nanoscale grains with an average size of 50 nm. Increasing fraction of these grains with strain led to transition from DSRX to continuous GG under subsequent annealing. The different annealing behavior was attributed to strong strain dependence for the relationship between driving pressures, which were caused by the stored dislocations and the boundary energy.
Numerical Simulation and Experimental Investigation of Grain Refinement Behavior in Equal Channel Angular Pressing/Extrusion Process
Authors: Xu Shu Bo , Ren Guo Cheng , Wang Gui Qing , Liu Peng
Published: December 2010

The ultra-fine grained (UFG) materials have been widely investigated due to their mechanical properties such as super high strength and super high plasticity. The finite element simulation schemes are planned for the deformation mechanism of ECAP pressing. It will greatly affect the extrusion process when processing parameter changed such as die geometrical parameters and friction condition. It is considerable to determinate the range of die channel angle and die corner angle during ECAP process, and a moderate die corner angle is usually chosen. The friction condition of the ECAP should be lubricated as good as possible in the pressing on the basis of optimal die geometrical conditions. The ECAP process is a non-uniform shear deformation process in the cross-section of the workpiece for first-pass pressing. There have low angle grain boundaries along the cross-section of the grain microstructures. For the multi-pass pressing, although the pressing pass numbers are same, the processing routes were of important significance on the grain sizes and grain distribution and grain boundaries (GBs) orientations of workpieces. The formation mechanism of nanostructure was given for the ECAP through studying the deformation behavior and dislocation’s evolution. The dislocation is one of the main defects in the processed materials, but the form of the dislocations and its density are difference for different processing route. The processed workpiece with high surface quality, refined grain microstructure and optimization grain boundaries were obtained with optimal processing parameters and routes.
The Influence of Texture and Grain Size on Compressive Deformation Behavior of Pure Mg through Equal-Channel Angular Processing
Authors: Li Ji Zhong , Ding Hua , Wu Xiao Lin , Xu Wei , Xia Kenong
Published: December 2010

Multi-pass of equal channel angular pressing (ECAP) at a single temperature as low as room temperature from 200 °C were measured using electronic back scatter diffraction (EBSD). The effect of texture and grain size on mechanical properties was investigated to realize the strengthening and large plastic deformation mechanism. A room temperature ECAP with multi-pass procedure is effective to product high strength and large plastic Mg, as a result of submicron grain structure and texture strengthening.
Microstructural Evolution of Mg-4Nd Alloy Processed by High-Pressure Torsion
Authors: Bai Jing , Xue Feng , Alhajeri Saleh N. , Langdon Terence G.
Published: December 2010

Disks of as-extruded Mg-4Nd alloy were processed by high-pressure torsion (HPT) through ¼ to 5 turns at room temperature. The first 1/4 turn of HPT induces large numbers of twins and some dislocation tangles in the center region of the disk. With increase of torsional straining, the twinning is inhibited gradually and the dislocation density increases relating to the formation of dislocation substructures and ultimately transforming to high fractions of equiaxed gains which have an average grain size of ~200 nm and high-angle boundaries. HPT significantly improves the values of microhardness of this alloy. The hardness values in both the central and edge regions show a sharp rise after HPT for 1/4 turn and exhibit nearly saturation after 1/2 turn although there is a trend of a slight increase with increasing numbers of turns. The experimental results suggest more homogeneous microstructures may be produced by larger numbers of turns in the HPT process.
Developing the Technique of Severe Plastic Deformation Processing through High-Pressure Torsion
Authors: Kawasaki Megumi , Langdon Terence G.
Published: December 2010

The processing of metals through the application of severe plastic deformation provides the potential for achieving exceptional grain refinement in bulk solids. Several SPD methods are now available but processing by high-pressure torsion (HPT) has attracted much attention over the last five years. Numerous reports are now available describing the application of HPT to a range of pure metals and simple alloys and excellent grain refinement were achieved using this process with the average grain size often reduced to the nanoscale range. However, in order to make this technique more practical, the nature of the sample characteristics immediately after conventional HPT must be considered in order to understand the fundamental principles of HPT processing. This report examines the procedure with special emphasis on the evolution in hardness homogeneity in both high-purity aluminum and a Zn-22% Al eutectoid alloy processed by HPT.
High-Temperature Severe Plastic Deformation of Ferritic Steel by Torsion
Authors: Setiawan Aries , Terada Daisuke , Tsuji Nobuhiro
Published: December 2010

An ultra-low carbon IF steel was heavily deformed up to an equivalent strain of 36 at various high temperatures of ferrite single-phase region and various strain rates. Effects of temperature and strain rate on the microstructures evolved in torsion deformation were clarified. On the other hand, it was found that homogeneous ultrafine grained structures were not obtained by the present torsion deformation though very high strain was applied. The coarser grain sizes than those obtained by conventional severe plastic deformation (like ARB) were due to the deformation at higher temperature and lower strain rate, but lower fraction of high-angle grain boundaries in the torsion specimen was suggested to be attributed to the characteristics of monotonic torsion (or simple shear) deformation including the way of strain evaluation.
The Structure of Nb Obtained by Severe Plastic Deformation and its Thermal Stability
Authors: Popov Vladimir V. , Popova E.N. , Stolbovsky A.V. , Pilyugin V.P.
Published: December 2010

Evolution of structure of Nb subjected to high-pressure torsion (HPT) with various strain at cryogenic and room temperatures and further annealing in the temperature range of 100-7000C has been studied by transmission electron microscopy (TEM) and microhardness measurements. HPT in liquid nitrogen enables to obtain true nanocrystalline structure with crystallite sizes of about 75 nm and the record-breaking microhardness of 4800 MPa. The thermal stability of the structure obtained is analysed.
Microstructural Evolution of Ultrafine-Grained Steel during Tandem Rolling Process
Authors: Huo Xiang Dong , Mao Xin Ping , Chai Yi Zhong
Published: December 2010

Titanium microalloyed steel whose grain size is around 3μm has been developed by CSP process. Samples after different plastic deformation were obtained by suddenly stopping the six-stand finishing train during tandem rolling. Experimental results and analysis show that plastic deformation during tandem rolling plays a major role for grain refinement. With the successive severe strain, microstructure of the same stock during tandem rolling is further refined because of repeated recrystallization at higher temperature and strain accumulation at lower temperature. Technological features of CSP process, such as large reduction per pass, rapid cooling after rolling and high solidification and of thin slab, are important reasons for obtaining ultafine-grained structure. Besides these, chemical composition of titanium microalloyed steel has beneficial effects on grain refinement.
Microstructures and Tensile Properties of Maraging Steel Processed by Equal-Channel Angular Pressing
Authors: Yang M.X. , Yang Gang , Liu Zheng Dong , Wang Cun Yu , Huang C.X.
Published: December 2010

An 18Ni (C-250) maraging steel was successfully processed by equal channel angular pressing (ECAP) for a single pass at room temperature. Microstructural observations showed that the martensite laths of 18Ni maraging steel were elongated to more narrow bands with a width of 100-200 nm after ECAP deformation. After ageing treatment, many nano-sized precipitates distributed uniformly within the refined martensite lathes. In comparison with the tensile strength (1940 MPa) of general used steel (solution + aging treatment), the tensile strength of the sample processed by ECAP and subsequent aging treatment was enhanced for more than 100 MPa (above 2050 MPa). The enhancement of tensile properties was attributed to microstructural refinement and uniformly distributed nano-precipitates.
Stabilization of Lattice Defects in HPT-Deformed Palladium Hydride
Authors: Bönisch Matthias , Zehetbauer Michael J. , Krystian Maciej , Setman Daria , Krexner Gerhard
Published: December 2010

Recent investigations on palladium hydride (Pd-H) showed, for the first time, evidence of formation of vacancy-hydrogen (Vac-H) clusters during Severe Plastic Deformation (SPD) effected by High Pressure Torsion (HPT). Vacancy concentrations produced in Pd-H by this method are extraordinarily high. DSC-scans show that the thermal stability range of vacancies is extended by about 150K due to trapping of hydrogen leading to the formation of vacancy-hydrogen clusters. Recent experiments give evidence that the mobility of the H atoms and/or the vacancies is conditional for the formation of Vac-H clusters during HPT. Results furthermore indicate defect stabilization by hydrogen trapping not only for vacancy-type defects but also for dislocations and grain boundaries.
Texture Manipulation in Commercial Purity Aluminum by Deformation Path Change from ECAP to Plane Strain Compression
Authors: El-Danaf Ehab , Soliman Mahmoud S. , Almajid Abdulhakim A.
Published: December 2010

Electron back scattered diffraction (EBSD) was used to document the microstructure and texture developed due to cross deformation of commercial purity 1050 aluminum alloy. The materials was first deformed in equal channel angular pressing die (ECAP) to one and two passes, via route BC and then deformed in plane strain compression (PSC) to two axial true plastic strain values of 0.5 and 1.0. The study provides a documentation of the evolution of microstructure parameters namely; cell size, misorientation angle, fraction of submicron grain size and fraction of high angle grain boundaries. These microstructure parameters were investigated on the plane normal to the loading direction in PSC (RD-TD). These microstructure parameters are compared to those achieved due to the ECAP process only. The ideal rolling texture orientations are depicted and crystal orientation maps were generated. The spatial distribution of grains having these orientations are revealed through these maps. The fraction of the main texture components for a 10o spread around the specified orientations is experimentally calculated and a quantitative idea on the evolution of microtexture is presented.
Enhancing the Efficiency of ECAP Processing in Particle Redistribution by Combination of Different Processing Routes
Authors: Zhang Wen Li , Liang Wei , Bian Li Ping , Jia Jun Hao
Published: December 2010

The redistribution of the precipitate particles in Al-5Mg-2.5Si alloy during equal channel angular pressing (ECAP) up to 8 passes in five different routes 8BA, 8BC, 8BC-UD2, 4BA+4BC and 4BC-UD2+4BC is studied. It is shown that route BC, which exhibits an isotropic strain process, is less efficient in particle redistribution compared to route BA and route BC-UD2. Route BA and route BC-UD2 are more effective for particle redistribution, but result in an anisotropy structure with orientated alignment of the particles, especially in the case of route BA. As a compromise, relatively homogeneous microstructures with particles dispersively redistributed are obtained by combination of different processing routes 4BA+4BC and 4BC-UD2+4BC.
Decomposition of Nanostructured Martensite in Cu-Al Alloys Processed by High-Pressure Torsion
Authors: Zhang Guo Fan , Sauvage Xavier , Wang Jing Tao , Gao Nong , Langdon Terence G.
Published: December 2010

The phase decomposition was investigated in Cu-Al alloys processed to a nanostructure condition by High Pressure Torsion (HPT). The microstructures are characterized by optical microscopy (OM), X-ray diffraction (XRD) and Atom Probe Tomography (APT). The results show that the’ → (1 + decomposition reaction begins in the early stage of annealing and it is much faster than in the coarse-grained state although there are similar phases after annealing.
Grain Refinement and Hardening Induced by Heavy Deformation Using Low Energy High Current Pulsed Electron Beam Surface Treatment
Authors: Grosdidier Thierry , Samih Y. , Allain-Bonasso Nathalie , Bolle Bernard , Zou Z.X. , Quin Y. , Hao Sheng Zhi , Dong Chuang
Published: December 2010

The low energy high current pulse electron beam (LEHCPEB) irradiation induces ultra fast dynamic temperature fields in the surface of the material to which is associated dynamic stress fields that causes intense deformation at the material surface and sub-surface. Improved surface properties (hardness, corrosion resistance) can be obtained using the LEHCPEB treatment. Under the “Melting” mode, the top surface (few µm) which is melted and rapidly solidified (107 K/s), can solidify has nano-domains formed from the highly under-cooled melt. The thermal stress wave that propagates in the sub-surface imposes strain hardening and grain size refinement. This induces a sub-surface hardening that can extent over about 100 µm. The use of the “Heating” mode is less conventional. This mode can promote grain size refinement, hardening as well as texture modification without modification of the sample geometry.
Mechanism Responsible for Dynamic Recrystallization for Repeated Plastic Working Deformation Process
Authors: Wang Xu Dong , Du Wen Bo , Wang Zhao Hui , Li Shu Bo
Published: December 2010

The repeated plastic working deformation(RPW) process can reduce grain size of a Mg alloy from 50-100 um to 10-500 nm, but the mechanism responsible for it has not been clear up to now. In the present paper, the effect of RPW deformation process on the grain size of Mg-5Gd-1Er alloy has been studied, and a series microstructural evaluations were performed to investigate the possible mechanism for RPW deformation by using transmission electron microscopy. Although there are no twinning or fibrous microstructures, the dynamic recrystallization, which usually occurs in high stacking fault energy metals, has been found in the alloy deformed by RPW process. The results indicated that the vacancy diffusion played an important role in this kind of dynamic recrystallization. According to the evolution of microstructure, a mechanism was proposed to explain the dynamic recrystallization for RPW deformation process.
Dispersion of the Structure in Al-Based Alloys by Different Methods of Severe Plastic Deformation
Authors: Brodova I.G. , Shirinkina I. , Petrova A.
Published: December 2010

Structural and phase transformations in V95 (type of A7075) alloy upon high pressure torsion (HPT) up to high strain and upon dynamic channel angular pressing (DCAP) were studied using electron microscopy (TEM, SEM) and x-rays diffraction. It was established that the nanostructure with average grain size of 80-55 nm and hardness value of 2.5 GPa is formed by HPT at strain of e=5.5-6.4. It was shown the hardening metastable phase MgZn2 precipitates from supersaturated α-solid solution during dynamic deformation aging; its quantity grows with increasing of strain. Ultra fine grained structure with high- angle boundaries is formed in V95 alloy after already 2 cycles of DCAP. The average grain size is 200 nm in DCAP samples.
Microstructure of Pure Ni Subjected to High Pressure Torsion
Authors: Zhang Hong Wen , Huang Xiao Xu , Hansen Niels , Pippan Reinhard
Published: December 2010

Plastic deformation leads to a structural refinement by introducing low angle dislocation boundaries and high angle boundaries in the initial coarse grains. To understand the mechanisms for the structural refinement and to establish the structure-strength relationship requires a precise characterization of key structural parameters, namely the boundary spacing and boundary misorientation angle. This study gives the results of such a characterization of pure Ni subjected to high pressure torsion (HPT) up to a strain of 300. The structural analysis was carried out by transmission electron microscopy in the longitudinal sample section in which the detailed structural features can be resolved. It is found that the microstructure in the HPT Ni samples is dominated by a lamellar structure. The spacing of the lamellar boundaries decreases and their misorientation angle increases with strain following a power law up to strain of 12, above which saturation is reached at a strain of about 34. The distribution of lamellar spacings normalized by their respective average values at each strain show an identical form. This scaling behavior is discussed also with reference to other metals and processing routes.
Effect of ECAP on the Dimensional and Morphological Characteristics of High Performance Aluminium PM Alloy
Authors: Bidulská Jana , Kvačkaj Tibor , Kočiško Robert , Bidulský Róbert , Grande Marco Actis
Published: December 2010

The main aim of this paper is to show how ECAP influences the porosity distribution of PM aluminium alloys. The dimensional and morphological characteristics of investigated materials were measured individually for each pore. A commercial ready-to-press aluminium based powder (ECKA Alumix) was used as material to be investigated. After applying different compacting pressures (400 - 700 MPa), specimens were debinded in a ventilated furnace (Nabertherm) at 400 °C for 60 min. Sintering was carried out in a vacuum furnace at 610 °C for 30 min. The specimens were ECAPed for 1 pass. When severe plastic deformation is applied, the stress distribution in deformed specimens causes the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores, determining a given value of the dimensional characteristics. Consequently, ECAP influences the porosity distribution in terms of the involved severe shear deformation and therefore influences the pore morphology.
Nanostructure Evolution in an Austenitic Stainless Steel Subjected to Multiple Forging at Ambient Temperature
Authors: Belyakov Andrey , Tsuzaki Kaneaki , Kaibyshev Rustam
Published: December 2010

Deformation behavior and structural changes were studied in a 304-type austenitic stainless steel subjected to large strain multiple forging at an ambient temperature. The number of forging passes was 10, leading to the total cumulative strain of 4.0. The yield stress rapidly increased to about 1000 MPa after the first forging pass and then gradually approached a saturation level of about 2000 MPa in large strains. The grain/subgrain size decreased to about 50 nm at total strain of about 2. This grain/subgrain size reduced a little upon further processing; and comprised 35 nm after a total strain of 4.0. The fast kinetics for grain refinement was associated with deformation twinning and strain-induced martensitic transformation. The both of them resulted in fast grain subdivision at relatively small strains.