bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the Mechanism of Restoration in Subtransus Hot Deformation of Ti-6Al-4V
Authors: Warchomicka Fernando , Poletti Cecilia , Stockinger Martin , Degischer Hans Peter
Published: January 2012

Titanium alloys are attractive for structural applications in the aerospace industry due to their high specific strength in comparison with other engineering materials. These properties are strongly related to the microstructure obtained during thermo-mechanical processes. The influence of the processing parameters on the microstructure is investigated to determine criteria for the control of the forming processes. Pre-forged specimens of alpha-beta Ti-6Al-4V alloy with elongated primary alpha grains are deformed below the beta transus temperature between 0.1 and 10/s of strain rate. Compression is carried out parallel and perpendicular to the preferential orientations of the primary alpha grains. The local strain within the compressed samples is determined by finite element methods and correlated to the microstructure observed there. The alpha content is affected by the temperature of deformation and the morphology of the alpha grains is influenced by the strain and strain rate. Specimens with previous primary alpha grains parallel to the compression axis show a rotation of the alpha grains which were oriented almost perpendicular to the load axis. EBSD measurements are used to determine the restoration mechanism involved during hot deformation. Continuous dynamic recrystallization in the alpha grains is revealed by increasing the cumulative crystallographic misorientation towards the grain boundary and the formation of new grains. This misorientation increases with increasing values of the Zener Hollomon parameter (Z). For lower values of Z restoration occurs mainly in the beta phase.
Antifouling Stainless Steel Surface: Competition between Roughness and Surface Energy
Authors: Jimenez Maude , Hamze Hassan , Allion Audrey , Ronse Gilles , Delaplace Guillaume , Traisnel Michel
Published: January 2012

To increase the shelf-life qualities of dairy products, a heat treatment is usually done. However, heat treatments induce physico-chemical modifications of the products. Some of them lead to the expected product but an unwanted consequence of this process is the formation of a fouling deposit on the surfaces in contact with the processed fluid. To eliminate fouling, cleaning processes have to be done once a day. It increases the processing and maintenance costs. To control and to decrease the fouling are the main problems in food industries and an active research is carried out on efficient antifouling surface treatments. In the present study, a 316L 2B stainless steel was submitted to different surface treatments (Flame and plasma pre-treatments, Plasma Enhanced Chemical Vapour Deposition, hydrophobic coatings, mechanical polishing ...) to try to establish correlations between different surface parameters (roughness, hydrophobicity, nanostructuration, surface energy, ...) onto the fouling in heat exchangers. All the treated plates were then submitted to a fouling test using an aqueous solution of β-lactoglobulin at 1% (p/p) with a final calcium concentration of 910 mg/L and compared to a bare steel plate. The results obtained imply different influences of each parameter depending on the surface roughness: the effect of a non organized micrometric roughness is preponderant compared to the surface energy: the fouling comes from a mechanical effect mainly due to rubbing. However, when the surface is nanostructured, fouling decreases. When the roughness reaches the nanometer scale (between 100 and 400 nm), it is the surface energy and the polar/apolar components which become preponderant compared to the roughness. Fouling is this time mainly due to the hydrophilicity of the surface and to the adsorption of the β-lactoglobulin on acido-basic sites. Finally, when the roughness reaches less than 50 nm, polar/apolar components show no effect anymore, the preponderant parameter is the hydrophobicity of the surface.
Improving Releasability of Mold Materials for IC Encapsulation Using Epoxy Compounds
Authors: Kitaoka Satoshi , Kawashima Naoki , Yoshiya Masato , Miyagawa Shigeru , Noguchi Yoshinori , Ikemura Kazuhiro
Published: January 2012

The effect of dopants such as zirconium and nitrogen on the releasability of Y2O3-based ceramics from molds was investigated for integrated circuit packaging using epoxy molding compounds (EMCs). Co-doping of these elements was carried out by annealing the surfaces of 5mol% ZrO2-Y2O3 samples under a N2 flow at 1100-1300 °C, resulting in concentration of nitrogen near the surfaces of the samples. The adhesion strength was minimized by exposure at about 1200-1250 °C, which was less than half the value for the undoped Y2O3. The co-doping remarkably decreased the polar part of the surface energy and consequently hydrophobicity of the ceramic surfaces increased. The excellent releasability characteristics were likely related to the depression of dissociative adsorption of water molecules, which are considered to act as active sites for the adhesion of EMCs.
Preliminary Study on the Fretting Wear Reliability of an Annular Nuclear Fuel
Authors: Lee Young Ho , Kim Hyung Kyu
Published: January 2012

Recently, a dual-cooled fuel (i.e. annular fuel) which is compatible with current operating PWR plants has been proposed in order to increase both power densities and safety margins. Due to the design concept that is compatible with current PWR plants, however, when compared with a current solid nuclear fuel it shows a narrow gap between fuel rods and needs to modify spacer grid shapes and their positions. Because a flow-induced vibration by fast primary coolant is inevitable phenomenon, it is necessary to examine the fretting wear behavior between an annular fuel and designed spacer grids. In this study, fretting wear has been performed to evaluate the wear resistance of the annular fuel by using specially designed spring and dimple of spacer grids that have a cantilever type and a hemispherical shape, respectively. At the spring specimen with relatively small stiffness value, fretting wear was initiated at both end regions and then proceeded gradually to center region. Based on the test results, the fretting wear behavior of annular fuel was compared with the current solid nuclear fuel and a comparative factor of its reliability was proposed.
Superhydrophobic RTV Silicone Rubber Coatings on Anodized Aluminium Surfaces
Authors: Momen Gelareh , Farzaneh Masoud
Published: January 2012

A superhydrophobic surface was elaborated using two inexpensive industrial processes: surface anodization in phosphoric acid and spin coating of the anodized surface by RTV silicone rubber. Scanning electron microscopy (SEM), atomic force microscopic (AFM) and water contact angle measurements have been performed to characterize the morphological features, and wettability of the surfaces. The water static contact angle of the elaborated surface reached 157 ° at room temperature. At supercool temperature (-10°C) the superhydrophobic coating showed an important delayed freezing time.
Laser Cladding of Nickel Alloy with Ceramic Nanopowder on Steel as Coating in Corrosive Media
Authors: Pérez A. T. , Montealegre Maria Angeles , Arias J.L. , Castro Regal Gemma , Rey P. , González M. , Bouzada F.
Published: January 2012

There is a need in different industry sectors to improve the performance of material surface under corrosive environments, which cannot be fulfilled by conventional surface modifications and coatings. NiCrMoNb alloy is nickel alloy commonly used as coating in corrosive media at high temperatures. The aim of this work is to produce nickel alloy nanocomposite coatings on steel by laser cladding. They are obtained by laser melting blown powder on the steel surface. The powder precursor is obtained by mechanical milling of a NiCrMoNb alloy micropowder (20-63 μm) with yttria nanopowder (10-30 nm). A comparison between conventional nickel alloy laser cladded coating and nickel alloy with nanoparticles laser cladded coatings, regarding their microstructure, mechanical properties (hardness, wear resistance) and corrosion behavior, is established.
Mechanical Properties Enhancement of High Reliability Metallic Materials by Laser Shock Processing
Authors: Ocaña José Luis , Morales M. , Porro J.A. , Iordachescu D. , Díaz M. , De Lara L. Ruiz , Correa C.
Published: January 2012

Laser shock processing (LSP) is being increasingly applied as an effective technology for the improvement of metallic materials surface properties in different types of components as a means of enhancement of their corrosion and fatigue life behavior. As reported in previous contributions by the authors, a main effect resulting from the application of the LSP technique consists on the generation of relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Additional results accomplished by the authors in the line of practical development of the LSP technique at an experimental level (aiming its integral assessment from an interrelated theoretical and experimental point of view) are presented in this paper. Concretely, follow-on experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (especially Al and Ti alloys) under different LSP irradiation conditions are presented along with a practical correlated analysis on the protective character of the residual stress profiles obtained under different irradiation strategies and the evaluation of the corresponding induced properties as material specific volume reduction at the surface, microhardness and wear resistance. Additional remarks on the improved character of the LSP technique over the traditional “shot peening” technique in what concerns depth of induced compressive residual stresses fields are also made through the paper.
Chemical Spray Pyrolysis Path to Synthesis of ZnO Microsausages from Aggregation of Elongated Double Tipped Nanoparticles
Authors: Muiva Cosmas , Sathiaraj Stephen T. , Maabong Kelebogile
Published: January 2012

The versatile chemical spray pyrolysis was used to prepare elongated double tipped ZnO nanoparticles and microsausages on glass substrates. X-ray diffraction studies revealed several crystallographic plane orientations with the most predominant along the (002) direction. Scanning electron microscope (SEM) observations indicated double tipped nanoparticles with an aspect ratio of 4.5-8.6 which coalesced in regular patterns to form microsized sausages of width ranging up to 1.2 µm. The absorption mechanism was through direct transitions with an absorption edge corresponding to a band gap of 3.18 eV.
Powder Processing and Coating Heat Treatment on Cold Sprayed Ti-6Al-4V Alloy
Authors: Wong Wilson , Irissou Eric , Legoux Jean Gabriel , Vo Phuong , Yue Stephen
Published: January 2012

This study investigates the effect of powder processing on powder flowability, compact ability, and the heat treatment of the resulting coatings on the mechanical properties of cold gas dynamic sprayed Ti-6Al-4V alloy. Nitrogen gas was used throughout the coating deposition process. Propellant gas temperature and pressure were attuned to maximize particle impact velocity. Three powder processing conditions were used in this study: as received (AR), low-energy ball milled (BM), and argon atmosphere heat treated (HT). Results showed coating porosities of around 6 to 7%, regardless of the feedstock powder used or the heat treatment performed. It was observed at 600 and 800°C anneals that a coating hardness reduction occurred, possibly due to static recovery and recrystallization, with minor sintering possibly occurring at the 800°C anneals. In addition, micro tensile tests showed an increase in cohesion strength at higher heat treatment temperatures.
Nitriding of Ternary Iron-Based Alloys: Metastable Mixed Nitrides, Excess Nitrogen and Stress-Depth Profile
Authors: Schacherl R.E. , Mittemeijer Eric Jan
Published: January 2012

For the first time it could be shown that, upon nitriding Fe-Cr-Al alloys, the thermodynamical stable cubic CrN and hexagonal AlN nitrides do not develop. Instead, a mixed CrxAl1-xN nitride develops of rock-salt crystal-structure type exhibiting a Bain orientation relationship with the ferritic matrix: the Al atoms are “dragged” into the developing cubic CrN precipitates. Similar observations were made upon nitriding Fe-Cr-Ti alloys. The formation of these mixed CrxAl1-xN precipitates is associated with the incorporation of large amounts of (mobile and immobile) “excess nitrogen” and the development of large residual stresses. Creep, associated with residual stress relaxation, occurs during nitriding, giving rise to complex residual stress-depth profiles.
Caracteristics of TiN Coating Films for Large Sizes Prepared by Arc Ion Plating
Authors: Baek Kyeong Cheol , Seo Chan Yeol , Heo Ki Bok , Kim Yang Soo , Yoon Dong Joo , Kim Byung Il , Lee Kyung Ku , Han Dong Soo
Published: January 2012

Arc ion plating (AIP) is one of the most attractive physical vapour deposition (PVD) method for the industrial manufacture of TiN coatings, owing to a high degree of ionization in the target material and convenient control of the process parameters. The important characteristic of hard coating is the adhesion strength between the coating layer and the substrate. The coating will be subjected to various loads, such as mechanical, thermal load, etc., in practical applications. Therefore, for more than a decade, Ti-based hard coatings have been applied to tools, dies, and mechanical parts because of the enhance lifetime and performance. It is focus on the attractive properties such as high hardness, good wear, and chemical stability. In the present study, TiN monolayer film was prepared at various N2 partial pressures and current by the AIP technique in SACM645 material. The correlation between microstructure and properties of the TiN coating was comparatively investigated by XRD, FE-SEM and AFM. These study carried steadily out improve the adhesion properties and wear resistance of Ti-based coating using pre-treatment of the substrate, insertion of an interlayer, application of multi-layers and adjustment of the process parameters. The main phase FCC TiN displayed (200) orientation in the film with the highest N2 partial pressure. The (111) orientation was observed with decreasing N2 partial pressure. The (200) and (111) textures in the film which was treated 80A arc current were found to be competitive orientations, however stronger arc treated the (200) texture was increased. The multilayer TiN films has possessed high hardness (up to 42Nm) and the best wear resistance among the specimens. These features were attributed to the presence of dense microstructures that were mainly composed of TiN phase around 5.16㎛ thickness, HF1 adhesion and Ra 35㎚ surface roughness
Correlation between Tribological Properties, sp²/sp³-Ratio and H-Content of Low-Wear Diamond-Like Carbon (DLC) Layers
Authors: Vogli E. , Hoffmann Fabian , Bartis E. , Oehrlein G. S. , Tillmann Wolfgang
Published: January 2012

It has been established that hardness and density of diamond-like carbon (DLC) layers can be raised by increasing ion energy during deposition, decreasing H-content and by increasing sp3-fraction. To confirm differences in hydrogen content of hydrogen containing and hydrogen free DLC films deposited at different bias voltages, layers were etched in oxygen atmosphere in a capacitively coupled plasma device. By employing real-time ellipsometry measurements, the H-content of the hydrogen containing a-C:H layers were estimated by determining the optical constants n and k (n-real part and k-imaginary part of the refractive index). In addition, DLC layers were analyzed by X-ray photoelectron spectroscopy to estimate the ratio of sp²- and sp³-hybridization. The mechanical and tribological properties of the coatings were evaluated by means of nanoindentation and ball-on-disc-tests. Finally correlations between these properties, H-content and sp3/sp2-ratio were obtained in an effort to explain different tribological behaviors of DLC-layers.
Effect of Trench Aspect Ratio on Microstructure and Texture in Damascene Cu Interconnects
Authors: Chen L. , Yuan G.J. , Xu J.G. , Guo F. , Pang N.
Published: January 2012

The effect of trench aspect ratio and line spacing on microstructure and texture in annealed damascene Cu interconnects has been investigated. The X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analyses of Cu lines, showed a preferred {111} orientation and the trenches reduce the proportion of high-angle grain boundaries and increase the fraction of coincidence site lattice (CSL) grain boundaries, comparing with the Cu blanket film. In addition, both trench aspect ratio and line spacing can largely affect the microstructure and texture in annealed damascene Cu interconnects.
Effect of Electric Field Strength on Texture Evolution of IF Steel Sheet during Annealing
Authors: He Chang Shu , Zhao Xiang , Tong Wei Ping , Zuo Liang
Published: January 2012

Specimens cut from a cold-rolled IF steel sheet of 1 mm thickness were respectively annealed at 750°C for 20min under a range of DC electric fields (1kV/cm~4kV/cm). The Effect of electric field strength on recrystallization texture of IF steel sheet was studied by mean of X-ray diffraction ODF analysis. It was found that γ-fiber textures were notably enhanced as electric field strength increased. The strength of γ-fiber textures got their peak values as the applied electric field reached to 4kV/cm. The possible reason for such phenomena was discussed in the viewpoint of interaction between the applied electric field and the orientation-dependent stored-energy in deformed metals which is known as the driving force for recrystallization during annealing.
Influence of Heating Rate and Decarburization Temperature on the Microstructure and Magnetic Properties of Grain Oriented Electrical Steel
Authors: Hou Chun Kan , Tzeng Jian Ming
Published: January 2012

Effects of three heating rates, 5, 20/min., and 300°C/sec and decarburization temperature, 700-850°C in primary annealing on the microstructure and magnetic properties of a grain oriented electrical steel were investigated. It was found that the oxide layer thickness and grain size increased with increasing decarburization temperature. However, they decreased with increasing heating rate. On the other hand, injection nitrogen content into steel sheets decreased with increasing decarburization temperature. The percentage of abnormal grain growth obtained a peak value at 800°C in the specimens treated with heating rate less than 20°C per minute. But specimens with rapid heating rate, percentage of abnormal grain growth increased with increasing decarburization temperature. As percentage of abnormal growth increased, magnetic properties got better.
Microstructure and Texture Evolution of Fe-Si Steels after Hot Dipping and Diffusion Annealing
Authors: Danzo I. Infante , Verbeken Kim , Houbaert Yvan
Published: January 2012

A homogenous intensity distribution along the cube texture fibre is important to achieve an easy magnetization in non-oriented electrical steels. Several alternatives have been discussed in literature to achieve this goal namely, tertiary recrystallization (surface energy controlled), decarburization annealing, two step cold rolling (strain induced boundary migration), twin-roll thin strip casting (directional solidification), phase transformation (surface energy anisotropy) and columnar grains formation (selective grain growth). In the present study, a hypoeutectic Al-Si alloy was deposited on the surface of cold rolled Fe-Si steels with a hot dipping simulator and subsequently annealed at 1000°C for different times. This procedure was developed previously in order to enrich the substrate with Al and/or Si and consequently improve their resistivity. Of specific interest was the formation of columnar grains in the low Fe-Si steel after annealing. These columnar grains were found to grow from the surface towards the centre of the substrate. The microstructure and texture in the columnar grains were significantly different than those in the middle of the material. Therefore, the evolution of these features during processing was studied in detail in this work.
Microstructure and Mechanical Properties of Spray-Deposited Zn-30Al-1Cu Alloy
Authors: Wang Feng , Xiong Bai Qing , Zhang Yong An , Liu Hong Wei , Li Zhi Hui , Li Xi Wu
Published: January 2012

In this study, Zn-30Al-1Cu alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the alloy were studied using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. It can be seen that the microstructure of spray-deposited Zn-30Al-1Cu alloy is composed of the Zn/Al eutectoids and few compounds. The Zn/Al eutectoids were shown lamellar, particle and Chinese script morphologies. The compound phases in the microstructure of the spray-deposited alloy were examined. The property test results indicate that the spray-deposited Zn-30Al-1Cu alloy displays superior tensile strength.
Numerical Model of Microstructure and Fracture of Coated Aluminum Alloys: A Novel Design Approach
Authors: Rashwan Ola , Stoilov Vesselin
Published: January 2012

Al/Si alloys are considered to be one of the most promising light weight alloys that can be used extensively in aerospace and automotive industry except for the poor tribological behaviour. However, with advancement and precision of the surface coating depositing techniques, new coating design which significantly enhances the tribological properties of the light weight alloys becomes attainable. In this paper, an innovative coating design is presented and thoroughly analyzed using finite elements method. The proposed model consists of Al/Si 319 as a matrix within which the geometrically defined hard Si particles are dispersed on the surface, and a hard coating layer then deposited in between the Si particles so that the lateral movement of the Si particles is constrained. ABAQUS is utilized to model and address the effects of different parameters, such as coating material, the hard coating thickness, and geometrical shape of the Si particles on the fracture and deboning of the entire structure. Two Si particles shapes are studied: circular and elliptical. Three coating materials are investigated: DLC, CrN and Al2O3. Besides, four coating thicknesses of 4 µm , 8µm, 15µm and 20µm are tested. It is found out that there is no single significant parameter which affects the fracture and deboning of Si particles, yet it is the combination of different parameters. The Si particle geometry plays a major role in determining the critical fracture stress with a circular shape outperforms the elliptical shape. The combination the circular Si particles and the CrN as coating material gives the highest critical fracture stress. Finally, DLC does not perform well with the circular Si Particle and it show the highest possible fracture stress with elliptical Si particle
Influence of Surface Micro Texture on Photocatalitic Function of Titanium Dioxide Film
Authors: Shimizu Jun , Kobayashi Go , Hasegawa Naomi , Yamamoto Takeyuki , Ojima Hirotaka , Onuki Teppei , Zhou Li Bo
Published: January 2012

This study aims to develop a high-functional photocatalytic film, of which surface is regularly textured by the micro machining technique in order to earn the real surface area. In this work, a regularly textured TiO2 film surface was fabricated by anodic oxidizing a pure titanium plate with regularly arrayed micro cutting grooves, and its wettabilty was evaluated. Micro cutting grooves were machined by a 3-axis NC control precision machine tool with a single point diamond cutter. Anodic oxidation experiments were conducted by using the self-developed equipment with diluted acetic acid as the electrolyte. As a result, it was found that the wettability of the TiO2 film surface regularly textured by synchronized 3-axial micro cutting was superior to those of the mirror finished or irregularly textured surfaces under the irradiation environment by the ultraviolet rays.
Microstructure and Texture Development in Pure Ta Sheets Processed by Conventional Rolling and Cross Roll Rolling
Authors: Song Kuk Hyun , Kim Han Sol , Kim Won Yong
Published: January 2012

To evaluate the effect of rolling process on microstructures and textures development, this work was carried out using pure Ta sheets. For this work, conventional rolling (CR) and cross roll rolling (CRR) as a deformation process were introduced, pure Ta sheets were cold rolled to 90% in thickness reduction. After this, to obtain the recrystallized microstructure on cold rolled materials, the recrystallization heat-treatment was performed at 1200°C for 60 min under the high vacuum state. Also, to analyse the grain boundary character distributions of the annealed sheets, electron back-scattered diffraction method was introduced. As an experimental result, increase in strain rate led to the development of texture with its texture component of <111> at conventional rolling and cross roll rolling, in common. Therefore, in this study, we systematically discussed the texture development due to increase in effective strain.
Texture Evolution in Nanocrystalline Fe Induced by Surface Mechanical Attrition Treatment
Authors: Chen Wei Ye , Tong Wei Ping , He Chang Shu , Zhao Xiang , Zuo Liang
Published: January 2012

The texture evolution of the pure iron sample after the surface mechanical attrition treatment (SMAT) was investigated by means of electron backscattering and X-ray diffraction (XRD) analysis. Experimental observations indicated that four sections along depth were formed in the pure iron sample during the SMAT, i.e., nanostructured regime in the surface layer, submicro-sized, micro-sized and plastic deformed regime. Compared to the microstructure of sample, texture analysis was performed. It can be found that the <110>//ND fiber texture is the prominent texture. A strong orientation of (110)[11] along the <110>//ND fiber was formed in the plastic deformed regime, and as the depth from the top surface decreases, <110> //ND fiber texture intensity increases. The maximum intensity was reached in the micro-sized regime, and then it start to reduce. In the nanostructured regime, <110> //ND fiber texture nearly disappear.
Crystallographic Behaviors of Uni-Axial Deformed High Manganese Steels
Authors: Yang Ping , Lu Fa Yun , Liu Tong Yan , Meng Li , Mao Wei Min
Published: January 2012

High manganese TRIP/TWIP steels with different Mn contents were subjected to uniaxial deformation. The textures, misorientations and orientation relationships were determined in austenite, HCP/BCC martensites and ferrite. It is observed that the mechanically stabilized austenite possesses mainly stable deformation texture, the intermediate HCP martensite possesses mainly unstable tilted basal texture and the BCC martensite possesses stable deformation texture which was actually mixed with transformation texture. Special misorientations due to either the inherence from austenite or due to twins or variant selection were main components in each phase. K-S relationship became much scattered due to slip-induced misorientations both in martensite and in parent austenite.
Effects of Magnetic Field Intensity on Microstructure and Orientation of Proeutectoid Ferrite in Fe-C Alloy
Authors: Zhang Xiao Xue , Zhang Yu Dong , Wang Shou Jing , Esling Claude , Zhao Xiang , Zuo Liang
Published: January 2012

The effects of the magnetic field intensity on microstructure and crystallographic orientation of proeutectoid ferrite in Fe-0.36C alloy have been investigated. Results show that the amount of the Widmänstatten ferrite decreases with the increase of the magnetic field intensity. The transformed proeutectoid ferrite tends to elongate and align along the field direction due to the magnetic dipolar interaction. This tendency is more pronounced when the field intensity increases. Moreover, the enhancement of the <001> fiber component along the traverse field direction by magnetic field is obvious when the field intensity is stronger.
3D Image-Based Stereology
Authors: Adachi Yoshitaka , Ojima Mayumi , Sato Naoko , Wang Yuan Tsung
Published: January 2012

The features present in 3D structure have geometric properties that fall into two broad categories: topological and metric. Metric properties are generally the more familiar; these include volume, surface area, line length and curvature. Equally or even more important in some applications are the topological properties of features. The two principal topological properties are number per unit volume and connectivity. In the present study, a change in morphology of pearlite and dual phase microstructures was examined from differential geometry and topology viewpoint. 3D images of eutectoid pearlite and dual phase steels were obtained by reconstructing serial sectioning images. Their metric and topological features were evaluated using The Euler Poincare formula and The Gauss-Bonnet Theorem. In addition, newly developed fully-automated serial sectioning 3D microscope “Genus_3D” will be also introduced.
Two Novel Methods to Realize the Superplastic Forming of Ultrahigh Strength Steels
Authors: Bai Bing Zhe , Zhang Han
Published: January 2012

Two novel methods of obtaining microduplex structures, ferrite plus spherical carbides, in ultrahigh strength steels (~2000MPa) are introduced. One is through an adequate deformation just below the austenite-ferrite equilibrium transformation temperature (i.e. Ae3 temperature, ~983K) followed by water quenching. The adequate deformation directly leads to the formation of a (ferrite plus spherical carbides) microduplex structure. The microstructure evolution during the deformation includes pearlite transformation, cementite spheroidization and ferrite recrystallization. The other is through an adequate deformation above Ae3 temperature (~1003K) followed by water quenching to produce martensite firstly and then obtain a (ferrite plus spherical carbides) microduplex structure during warm deformation of martensite. Microstructural analysis on the microduplex structure shows that submicron carbides are located at ferrite grain boundaries while nanometer ones are dispersed inside ferrite grains. This kind of carbide distribution may suppress the coarsening of ferrite grains and form a dynamic equilibrium of ferrite grain size on a specific deformation condition. The strain rate sensitivity of the (ferrite plus spherical carbides) microduplex structures is about 0.4 at 973K and strain rate of 10-4s-1.
Obtention of an Al-Based Composite Material by Direct Fusion of Used Beverage Cans
Authors: Carrasco Claudia , Montalba C. , Camurri Carlos
Published: January 2012

In the present study, the fabrication of an Al-based metal matrix composite material obtained directly from the melting of the aluminium used beverage cans in a modified rheocasting process is presented. The analysed operational condition is the shear rate applied to the bath and its influence on the properties of the obtained samples. Additionally, samples were heat treated at two different times. The characterization of the phases obtained in Al-based MMC was made by means of metallography, scanning electron microscopy with energy dispersive spectroscopy and electron microprobe with wavelength dispersion spectroscopy. The results show that some constituents were formed during the fabrication process of the MMC, mainly Al6(Fe, Mn), which are partially transformed during the heat treatment. Additionally, samples were evaluated using dynamic mechanical analysis, and the results suggest that the obtained MMC could have very good mechanical properties, similar or superior to the aluminium alloys commonly used for structural applications such as 6XXX family.
Determination of the Non-Recrystallisation Temperature (Tnr) of Austenite in High Strength C-Mn Steels
Authors: Gautam Jai , Miroux Alexis G. , Moerman J. , Barbatti Carla , van Liempt Peter , Kestens Leo A.I.
Published: January 2012

In the present study non-recrystallisation (Tnr) and Ar3 temperatures have been determined for the C-Mn steels from multi-pass hot torsion experiments with continuous cooling in the temperature range of 1260°C to 600°C. Results show that Tnr decreases with increasing strain/pass, strain rate or interpass time. An alternative approach based on the work-hardening rate is proposed for the determination of Tnr and is shown to be more suitable in case the usual mean flow stress method does not provide a clear Tnr value.
Transformation of Deformed Austenite at Temperatures above the Ae3
Authors: Jonas John J. , Basabe Vladimir V. , Ghosh Chiradeep
Published: January 2012

Recent observations regarding the transformation of deformed austenite are reviewed. It is shown that superequilibrium ferrite and pearlite can be formed at temperatures well above the Ae3 and Ae1, respectively. The role of the stored energy associated with the introduction of the dislocations introduced by the deformation is discussed. It is shown that the forward dynamic transformation into ferrite and pearlite is several orders of magnitude faster than the reverse static transformation back into austenite. The retarding effect of alloying additions such as niobium is also outlined. The results are interpreted in terms of the effect of deformation on the modified phase diagrams pertaining to the transformation of deformed austenite.
Modeling Alloying and Thermomechanical Processing Effects on the Austenite Decomposition Kinetics and Final Microstructure of Line-Pipe Steels
Authors: Khlusova Elena , Zolotorevsky Nikolay Y. , Vasilyev Alexander A. , Titovets Yuri F.
Published: January 2012

A mathematical model was developed predicting the effects of alloying and thermomechanical processing on the final microstructure of steel. Various factors influencing transformation kinetics, including microalloying with Nb and plastic deformation of austenite, are considered. Subsequent stages of the model development and calibration are described.
New Trends and Technologies in Thin-Slab Direct Rolling: Improved Microstructure & Mechanical Behavior
Authors: Klinkenberg Christian , Bilgen C. , Rodriguez-Ibabe J.M. , López Beatriz , Uranga Pello
Published: January 2012

The use of CSP® thin slab casting followed by direct thermomechanical rolling is well placed for the production of low-carbon Nb microalloyed steels. In this process thin slabs of between 48 and 90 mm thickness are cast and directly hot rolled to hot strip typically between 1 and 12 mm thick. To obtain optimum strength and toughness property combinations in a direct rolling process, hot rolling has to compact the dendritic as-cast microstructure and to achieve a fine-grained microstructure. This affords a two-stage rolling strategy with start rolling above the recrystallization stop temperature and finish rolling in the non-recrystallization temperature range. Temperature and deformation in the first stand should be as high as possible in order to delete the initial as-cast microstructure by complete recrystallization. Based on these considerations, SMS Siemag further developed the CSP® concept including features allowing isothermal rolling in the first stands of the finishing mill. The present contribution gives the results of a laboratory study of this innovative approach. The report concludes with resulting new plant configurations for improved high strength and API linepipe grade production.
A Review of the Stress-Relaxation Method for Following the Kinetics of Precipitation, Recovery and Recrystallization
Authors: Liu W.J.
Published: January 2012

Stress-relaxation method was first used by Liu and Jonas in 1980s for following the kinetics of strain induced precipitation of carbonitrides in austenite. Since then, the method has been widely employed for studying not only the precipitation kinetics but also the recovery and recrystallization processes in steels and other alloys. In the present paper, the principle and the worldwide usage of the method were reviewed. The dependence of stress relaxation rate on the occurrence of precipitation, recovery and recrystallization was interpreted based on a dislocation model. The capabilities and the limitations of the method were discussed and ways to overcome the existing limitations were also proposed.
Static Softening Behaviour in High Aluminum Steels
Authors: Aretxabaleta Z. , Pereda Beatriz , Parker S.V. , López Beatriz
Published: January 2012

The effect of Al addition on the static softening behavior of C-Mn steels was investigated. The compositions of the steels studied are representative of the recently developed TRIP-assisted steels: a base composition of 0.2%C, 2%Mn, 50ppm N and three different Al levels, 0.03 (base steel), 1 and 2%. Double-hit torsion tests were performed at different deformation temperatures, in the range 950°C to 1100°C, and pass-strains, =0.2 and 0.35. It was found that solute Al produced a significant retardation on static recrystallization kinetics, equivalent to that exerted by 0.026%Nb for the 1%Al steel and to 0.05%Nb for the 2%Al steel. Additionally, at the lowest temperatures (950-1000°C) and 2%Al level, austenite to ferrite phase transformation was found to be concurrent with softening, enhancing retardation in the mechanical softening.
Simulation of Hot Rolling Processing of an Al-Cu-Mg Alloy by Torsion Tests
Authors: Carreño Fernando , Cepeda-Jimenez Carmen , Peñalba Felix , Carsí Manuel , Ruano Oscar
Published: January 2012

Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted to failure in the range 270 to 470°C, between 2 and 26 s-1. A peak ductility of the 2024 alloy was found at about 410°C. The high temperature data was analyzed by means of a Garofalo equation, obtaining a stress exponent of 6.1 and an activation energy for deformation of 180 kJ/mol. These high temperature deformation parameters correspond to an underlying deformation mechanism of constant substructure (n=8) but experiencing increasing microstructure coarsening with increasing temperature. The workability of the alloy was characterized by maximum energy efficiency and stability maps constructed from the torsion tests data to determine optimal conditions for the forming process, which depend on applied strain rate. A forming temperature of about 400°C is recommended.
Rapid Spheroidization and Grain Refinement Caused by Thermomechanical Treatment for Plain Structural Steel
Authors: Mašek Bohuslav , Jirková Hana , Kučerová Ludmila
Published: January 2012

The cold formability of ferritic-pearlitic steels is one of the base parameters for material choice for different forming parts. One of the key factors is the pearlite morphology, which is strongly dependent on chemical composition and previous treatment history. The carbides in pearlite occur mainly in the lamellar form. One of the ways of improving the ductility along with formability is the change of lamellar carbides to globular carbides. This can be conventionally done by soft annealing, which is characterised by long processing times and high energy costs. This paper presents a new processing modification which can lead on the one hand to significant shortening of carbide spheroidization times and on the other hand to intensive refinement of grain size even for low-carbon steels. Low temperature thermomechanical treatment with variation of the heating temperature around Ac1 and incremental deformation was examined on low carbon plain RSt-32 steel. After the thermomechanical treatment conditions were optimized, the refinement of the ferritic grains from an initial 30 μm to circa 5 μm took place, and the time necessary for carbide spheroidization was shortened from several hours to several seconds.
Behavior of Pearlite in ThermoMechanical Processing and Service-Historical Perspective
Authors: McQueen H.J.
Published: January 2012

After 1780, wrought iron (WI) provided a structural material and steel was cherished for its hardness and cutting qualities. When available in quantity after ~1860, steel’s structural strength and wear resistance were recognized in normalized condition in armor plates, rails and drawn wire. The responsible microstructure component was pearlite in which the lamellar spacing of ferrite and carbides could be refined by simple bulk heat treatments that are practiced with small modification until today. The strength and toughness rose as the layer thickness decreased the ferrite slip length and the carbide cracking. In hot working, the strength rises as much as 200% (while ductility falls) with fraction of pearlite; below the transus compared to austenite just above it, strengths are equal at about 0.7C (ductilities equal at 0.35C).
Microstructure Modelling of Solid-State Transformations in Low-Alloy Steel Production
Authors: Mecozzi Maria Giuseppina , Bos C. , Sietsma J.
Published: January 2012

In this work the formation of microstructural banding in a dual-phase steel is investigated by using a three-dimensional cellular automata model for phase transformations. Originally developed for describing the metallurgical processes occurring during the annealing stage of cold-rolled strips, this model is presently applied to investigate microstructural-band formation during the austenite-to-ferrite transformation kinetics during cooling after hot rolling. The recent incorporation in the model of an inhomogeneous concentration of Mn, the alloying element most responsible for the development of microstructural banding, and the local nucleation behaviour dependent on the Mn concentration allows the study of the effect of material and process parameters on the banding formation.
Development of Asymmetric Rolling for the Better Control over Structure and Mechanical Properties in IF Steel
Authors: Orlov Dmitry , Lapovok Rimma , Tóth László S. , Timokhina Ilana B. , Hodgson Peter , Bhattacharjee Debashish , Haldar Arunansu
Published: January 2012

In the present study, the effects of kinematic and geometric asymmetries in rolling during multi-pass processing of IF steel are examined. The theoretical investigation by final element simulations and experimental investigations by means of electron-backscatter diffraction analysis and tensile tests suggest that asymmetric rolling increases the total imposed strain compared to symmetric rolling, and largely re-distributes the strain components due to additional shear. This enhances the intensity of grain refinement, strengthens and tilts crystallographic orientations, and increases mechanical strength. The effect is highest in the asymmetric rolling with differential roll diameters.
Hot Deformation Behaviour of Low Alloyed Steel
Authors: Poletti Cecilia , Großeiber S. , Ilie Sergiu , Degischer Hans Peter
Published: January 2012

Hot deformation of a continuously cast low alloyed steel is studied by means of hot compression and tensile tests carried out after austenitization between 700–790 °C at 3x10-4 – 0.3 s-1 of strain rate. The ferrite transformation at the applied cooling rate was determined at 710°C by means of dilatometry. The compressive flow data obtained by using a Gleeble®1500 machine are evaluated to obtain the strain rate sensitivity and the processing maps using different models. The tensile data are used to determine the ductility of the material with different deformation parameters. A new calculation method is used for the instability parameter derived from the dynamic materials model. The strain rate sensitivity does not predict any instability but all the others instability parameters do, including the new one. Pores are formed at the prior austenitic grain boundaries at low strain rates, causing a decay of ductility in the tensile samples. A minimum in the ductility was observed for low strain rates at 750°C. Low strain rates and low temperatures increase the formation of more ferrite than without deformation at the corresponding heat treatments without deformation. In these conditions, the deformation is concentrated in the softer ferrite phase. Low power efficiency was calculated at high strain rates, where no dynamic recrystallization takes place. The domains with similar efficiency of power dissipation are correlated to deformation induced ferrite formation and ferrite recovery. These domains vary with the increasing strain.
Processing and Microstructure of Grain Non-Oriented Electrical Steel Strips with Improved Magnetic Properties
Authors: Salinas-Rodríguez Armando , Gutiérrez-Castañeda E.
Published: January 2012

The effects of annealing prior to cold rolling on the microstructure and magnetic properties of a low-C grain non-oriented (GNO) electrical steel strip have been investigated. It is shown that annealing of the hot-rolled strips in the intercritical region, Ac13, causes rapid decarburization and development of large columnar ferrite grains. This microstructure leads, after cold-rolling and a fast annealing treatment at temperatures between 800 and 850 °C, to a polygonal ferrite grain microstructure with magnetic properties superior to those observed typically in the same steel in the industrial fully processed condition. The results are attributed to the {100}-fiber texture developed during the final annealing. Annealing at T<800 °C or T>850 °C results in formation of {111}-fiber texture components due to recristallization or transformation of deformed ferrite leading to a negative effect on the final magnetic properties. The results suggest that annealing prior to cold rolling offers an attractive alternative processing route for the manufacture of fully processed low-C, Si-Al GNO electrical steels strips.
Effect of Magnetic Field Processing on Recrystallization and Grain Growth
Authors: Salvatori I.
Published: January 2012

In this paper the recrystallisation kinetics of cold rolled strips as a function of magnetic field intensity has been studied on a Fe-0.05C-1.5Mn alloy. The retarding effect on recrystallisation due to the application of a magnetic field on samples treated with magnetic field up to 10T, has been experimentally confirmed. The effect was more evident for high magnetic field and for long annealing times. In addition, a small retarding effect of magnetic field on grain growth has been noticed.
Advanced TMCP Steel Plates for Pipelines and Structurals
Authors: Schwinn Volker , Bauer Juergen , Fluess Peter , Amoris Eric
Published: January 2012

The developments of plates are strongly driven by demands from high-sophisticated pipeline and structural applications. Such needs reflect in plates with higher thickness, larger width, higher toughness also at lower temperatures, higher strength and/or better resistance to sour environments. The requirement profiles are, in some cases, exceptional and have become achievable, in an extreme combination of alloying and processing technologies, only as a result of comprehensive development work and plant investments. An outline of modern production facilities is given. A broad potential for innovation derives by the utilization of the key-technology TMCP (Thermo-Mechanical Controlled Process). As a central element to achieve high-class requirements, aspects and parameters of the metallurgical design are explained. The utilization is explained and illustrated with selected recent applications.