bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Processing Performance of Viscoelastic Abrasive Flow
Authors: Yang Lu , Zhang Ke Hua , Zheng Guang Zhen , Guo Hang
Published: March 2013

Abstract. Abrasive flow machining (AFM) is an advanced technology which can improve the uniform consistency of profiled surface. First, the dielectric characteristics of the abrasive flow (the medium features include medium types, medium viscosity coefficient, the concentration of medium and abrasive, abrasive type, abrasive size) is studied, abrasive flow including different medium is deployed by mixing and mix well of the polymer silicone fluid, silicone oil, wax, and other fats, and adding silicon carbide with different particle size and mixed for processing experiment. Within the limits of the workpiece polishing, the change direction of the surface roughness and the removal rate of workpiece surface are substantially same and approaching the linear relationship, the lowest surface roughness Ra of SiC (abrasive particle size is 200#) reduced from 3.5μm to 0.5μm. The hardness and durability of the silicon carbide abrasive in this study is quite good, and the price is low, the processing characteristics are quite consistent with the economic costs on the demand.
Experimental Investigations into Abrasive Flow Machining of Helical Gear
Authors: Xu Yong Chao , Zhang Ke Hua , Lu Shuang , Liu Zhi Qiang
Published: March 2013

Abstract. Abrasive flow machining (AFM) is an effective method that uses the flow of a pressurized abrasive media for removing workpiece material. It is used to deburring, polishing or radiusing, etc. In this paper, the effect that AFM process on the surface of the helical gear is investigated. Then, the distribution of the velocities, shear rates and shear forces of the abrasive flow on the helical gear surface is obtained by CFD module of the COMSOL Multiphysics software. The simulation results show that the abrasive grains near the addendum, tooth surface and tooth root can be subjected to corresponding shear stress. Experimental results indicated that the surface roughness Ra of the left tooth surface, right tooth surface and addendum before processing 1.429um, 1.108um and 2.732um dropped after processing 0.228um, 0.216um and 1.754um. All burrs at the intersection between tooth surface and end surface has been cleared, the surface quality of the helical gear has been improved. Therefore, AFM method can improve the surface quality of the helical gear effectively.
Research on Machining Virtual Reality System
Authors: Hu Q.N. , Feng D.J. , Shu H. , Dai H.Z. , Wu J.L.
Published: March 2013

A machining virtual reality system is established by studying the operating procedure of machining. The modeling and optimization method of scene model is put forward. Two different roaming ways, that is the automatic roaming path and the free roaming path, are designed. The process of machine and the operation of virtual worker are simulated based on the technique of modular programming and collision detection in Virtools, enhancing the sense of immersion and reality of the virtual machining process. The system provides a new method for machining experimental instruction.
Study on a High Frequency Resonance Fatigue Apparatus Using a Piezoelectric Vibrator
Authors: Jie Meng , Xie Hai Feng , Liu Yan , Yang Zhi Gang
Published: March 2013

In order to measure the fatigue property of the small and hard brittle components working under the condition of the little amplitude, high frequency force, a novel kind of high frequency resonance fatigue testing apparatus which driven by the piezoelectric vibrator is proposed. Firstly, the working principle of the apparatus is analyzed, and the dynamic model of the apparatus is established to get the systemic dynamic characteristics. Then a prototype is designed and produced. Finally, the maximum load on the sample is measured by the test. The results indicate that the maximum load on the sample is 75.1 N-172.5 N when the AC voltage amplitude (90 V-255 V) , thickness of the elastic loader (30 mm-45 mm)and the thickness of the plate spring (0.6 mm-1.2 mm) are changed. The prototype made in this paper is suitable for the tensile and fatigue testing with the load level mentioned above under the condition of little amplitude and high frequency force.
Characteristics Analysis of Acoustic Emission Signals from Tensile Process of High Pressure Gas Cylinder Materials
Authors: Lv Qiu Juan , Chen Min , Li Yan Jiao , Guo Zhi Qing , Liu Chang Jiang
Published: March 2013

Conducting tensile experiment with high pressure gas cylinder materials to analyze its acoustic emission (AE) signals, can realize the stretch features and AE signals regularity, which is very important to distinguish high pressure gas cylinder detection. The AE signals are divided into four different stages through the tensile experiment, which show that AE signals and theory analysis are fitted well and thus be used to distinguish materials defects.
A Unified Theoretical Framework to Model Bulk, Surface and Interfacial Thermodynamic Properties of Immiscible Liquid Alloys
Authors: Végh Ádám , Mekler Csaba , Kaptay György
Published: March 2013

Bulk, surface and interface thermodynamics of immiscible liquid alloys are considered within a unified theoretical framework. For bulk thermodynamic functions the exponential and the combined linear-exponential equations are discussed, obeying the 4th law of thermodynamics. Surface phase transition is discussed in details. For surface and interface thermodynamics the monolayer Butler equation is compared to the multilayer model. During further assessment of bulk thermodynamic data of immiscible liquid alloys their experimentally measured surface tension and interfacial energy should be also taken into account, coupled with the models presented here.
Comparison of Measured and Numerically Simulated Angular Velocity of Magnetically Stirred Liquid Ga-ln Alloy
Authors: Nagy Csaba , Rónaföldi Arnold , Roósz András
Published: March 2013

A measurement of the angular velocity/revolution number of magnetically stirred liquid gallium-indium alloy was realized with newly developed angular velocity measuring equipment. To get additional information about the flow of the melt, a numerical simulation model was performed with ANSYS FLUENT 13.0 with a single phase 2D k-ε turbulence solver. The aim was to reproduce the flow as accurate as possible, so the measured and computed angular velocity data was compared, to see if the system can be modeled fairly well.
Simulation of Grain Coarsening Using One-Dimensional Cellular Automaton
Authors: Gyöngyösi Szilvia , Barkoczy Peter
Published: March 2013

Numerous literature [1,4,5] has reported on the effective use of cellular automaton method for the simulation of short-range diffusion. Using this model for the simulation of short-range diffusional phase transformations therefore is a resolved issue. It is proven that two- or three-dimensional automata can reflect the course of the abovementioned processes realistically. What our study demonstrates more than in the past [1] is that two-dimensional stochastic cellular automaton simulation already presented before has been simplified. This time our automaton operates in one dimension [2], which has consequently reduced running time, thus, made it possible to enhance the efficiency of the scaling of simulation. In our previous work the results of scaling of one-dimensional simulation of the recrystallization process [3] were demonstrated, in our current study fitting is performed for measurement results of grain coarsening using one-dimensional cellular automaton.
The Effect of Technological Parameters on the Quality of UHMWPE Products
Authors: Kállai Imre
Published: March 2013

We can encounter products made from UHMWPE in many different areas of utilization. This material is used in plastic bearings, ball-and-socket joints, heavy-duty plastic cog-wheels and joint implants. The UHMWPE is a very particular polymer, the special characteristics of which can be attributed to its molecular structure. The ulra-high molecular weight has an effect on wear-resistance, creep-resistance and hardness. These are the parameters demanded by the highly specialized utilization. On the other hand, this molecular stucture also has disadvantages next to the many advantages. Its greatest disadvantage is that it’s difficult to process. The UHMWPE is a thermoplastic, but because of the long molecular chains its injection molding is impossible. In the course of the present research work we will compare the mechanical and quality properties of products made with lathe machining (RAM extrusion) and direct compression molding. We will examine the impact of the changes of the manufacturing and technological parameters. We will be placing a special emphasis on the surface quality because the quality and life-span of the abovementioned products (bearings, ball-and-socket joints, artficial joints) largely depends on this parameter. Besides this we will examine the changes of hardness and the stability of size. In view of these results we will try to determine what would be the best manufacturing technology that could ensure the maximum performance and life-span of these products. [1,3,6] We are focusing by having the results, to optimizing the manufacturing.
Tribological Testing Results Comparison by Microscope Techniques
Authors: Szívós Tamás , Zsoldos Gabriella
Published: March 2013

Ultra high molecular weight polyethylene (UHMWPE) was modified by 20 % methyl-methacrylate (MMA). Specimens were examined by two directional tribological wearing methods. Wear resistance of the modified materials was found to be increased by 38 %. Despite the promising results further experiments are needed to utilize it as human implant.
Hf Particles Reinforced Cu-Zr-Al Amorphous Powder Produced by Milling
Authors: Tomolya Kinga , Benke Márton , Janovszky Dóra , Kovács Árpád
Published: March 2013

This research work dealt with production of amorphous powder with nominal composition of (Cu55Zr45Al10)97Hf3 (at%). Combining the mechanical milling and alloying, powder of crystalline Cu-Zr-Al alloy mixed with Hf elemental powder were milled in order to produce a homogenous and amorphous alloy powder The master alloy and the powders milled for different time were analyzed by X-Ray Analysis (XRD) and Scanning Electron Microscopy (SEM). Particle size distribution and hardness were controlled during milling and at the end of procedure. The milling caused dissolving of the hafnium. The 25 h milling time was the optimal to obtain the Hf containing powder with amorphous structure. However, elemental Hf traces with size below 3 µm were still observed in the powder. After 50 h of milling, such impurity elements as iron, nickel, chromium originating from milling tools (vial, balls) were detected.
The Role of Pb Impurity in SAC Solder Alloy
Authors: Gergely Gréta , Molnár Alíz , Gácsi Zoltána
Published: March 2013

The European Union and Japan initiated the issue of RoHS, the directive about the restriction of hazardous substances, which prohibits certain hazardous substances in electronic equipment - including lead - application. Due to the directive the use of lead free solder alloys is spreaded, however the Pb in the form of contamination may be appear under technological process. The lead impurity has significant effect on microstrucutre and lifetime so it is necessary to carry out detailed examinations. In this paper the study of intermetallic compounds in six-element, Pb impured, thermal cycles test-subjected, Sn-Ag-Cu (SAC) solder alloy is demonstrated
Description of the PM Process by Using Ishikawa-Analysis
Authors: Simon Andrea , Kovács Károly , Gür C. Hakan , Pieczonka Tadeusz , Gácsi Zoltána
Published: March 2013

Composites are special material which can provide individual properties such as high strength with low density or good thermal conductivity with low thermal expansion coefficient. Composites conform to the constantly evolving and more complex expectations. In order to make a product with good quality, it is important to choose suitable materials and technology. In this research powder metallurgy (PM), as one of the most common composite manufacturing technology, was examined -which factors and mechanisms influence mostly the properties of the product. Ishikawa method was used to reveal these correlations.
The Constitutive Behavior of Al 7075 Aluminium Alloy under Hot Compression Test
Authors: Naser Tareg S. Ben , Krallics György
Published: March 2013

The constitutive equation in hot working for Al 7075 aluminum alloy was obtained employing experimental data of stress-strain curve, in a wide range of temperature (250-450°C) and strain rate (0.002-2 s-1). The influence of temperature and strain rate on the deformation behavior is represented by the equation proposed by Sellar and McTegart, all material parameters are considered as function of equivalent strain. The force-height data was corrected with interpolation method in the way to eliminate the error at the measurement. To verify the constitutive equation two parameter were calculated average absolute relative error (AARE=6.42) and correlation coefficient (R=0.998), for the same purpose the measuring and calculated flow curve are plotted together, the results shows that the constitutive equation obtained is good describing the behavior of the material.
Kinetics of Thermal Grooving during Low Temperature Recrystallization of Pure Aluminum
Authors: Zhang Yu Bin , Godfrey Andy , Jensen Dorte Juul
Published: March 2013

The migration of a recrystallization boundary in pure aluminum was followed during in situ annealing in a scanning electron microscope. The microstructure was characterized using the electron channeling contrast technique and a typical stop-go grain boundary motion was observed during annealing. The thermal grooving associated with boundary migration on the inspected free surface was characterized after the in-situ experiment using atomic force microscopy. The results show that new thermal grooves develop at places where the recrystallization boundary segments remain stationary for a relatively long time. The kinetics of thermal grooving are determined and effects hereof on the boundary migration are discussed.
Recrystallization and Grain Boundary Formation in an 18-Carat Gold Alloy Studied by Mechanical Spectroscopy
Authors: Maier Ann Kathrin , Tkalcec Iva , Mari Daniele , Schaller Robert
Published: March 2013

Heavily deformed 18-carat yellow gold samples show a recrystallization peak at 700 K during the first heating. The mechanical loss spectrum of polycrystals shows a relaxation peak at about 780 K, which is absent in single crystals made from the same alloy. Stepwise deformation of a single crystal from 2 % to 10 % causes an increase of the high temperature mechanical loss background and the appearance of a high temperature peak. At 8 % deformation the high temperature peak disappears and the peak that is normally observed in polycrystals appears. The increase of the exponential background is interpreted as due to the introduction of new dislocations whereas the high temperature peak is attributed to a relaxation mechanism in the sub grain boundaries. The peak of polycrystalline samples located at intermediate temperatures depends on the grain size: with grain growth, the peak position shifts to higher temperatures. The peak temperature can be related to the mean grain size.
Microstructural Control of Dual Phase Structure Formed by Partial Reversion from Cold-Deformed Martensite
Authors: Nakada Nobuo , Arakawa Yusuke , Park Kyo Sun , Tsuchiyama Toshihiro , Takaki Setsuo
Published: March 2013

Dual phase (DP) structure formed by partial reversion from cold-deformed martensite was investigated to improve mechanical property of DP steel by grain refinement strengthening. A low carbon martensitic steel (0.15C-1.0Mn) was cold-rolled and then held just above A1 temperature to partially form austenite. In particular, the conditions of cold-rolling rate (0~60% reduction in thickness) and heating rate (0.083 and 100 K/s) were varied to understand their effects on the microstructural development of DP structure. Although the recrystallization has never occurred in undeformed martensite, cold-deformed martensite was more easily recrystallized before reversion with increasing rolling rate and lowering heating rate. Then, the matrix of DP structure was changed from tempered martensite to recrystallized ferrite, which had a large influence on the distribution of fresh martensite transformed from reversed austenite. The higher rolling and heating rates resulted in the finer DP structure, leading to a large improvement in strength level.
Orientation Dependent Recovery in Strongly Deformed Al-0.1%Mn Crystals
Authors: Albou Adeline , Borbely A. , Maurice Claire , Driver Julian H.
Published: March 2013

Single crystals of Al-0.1%Mn have been channel-die compressed to a true strain of 2.3 and their recovery behaviour at 240-320°C investigated by microhardness measurements, EBSD microtexture mapping and X-ray line broadening analysis. The crystal orientations are the nominally stable Goss {110}, brass {110} and S {123}. For all three orientations the microhardness decreases with a logarithmic time dependency but the instantaneous recovery rates of the Brass oriented crystals are systematically lower than those of the other two orientations by a factor of about 2. The dislocation densities decrease rapidly in the first stages of recovery (<1 min) by dislocation dipole annihilation and more slowly thereafter. In the Goss and S orientations the later stage of recovery is due to sub-grain growth. The orientation dependency is ascribed to the relatively low misorientations developed by plastic straining in the Brass crystals (average about 4°) compared with the Goss and S orientations (about 7-8°).
Characterization the Softening Behavior of Cold Rolled AlMnFeSi-Alloys during Conditions of Concurrent Precipitation
Authors: Wang Ning , Li Yan Jun , Marthinsen Knut
Published: March 2013

In the present work an Al-Mn-(Fe-Si) model alloy has been subjected to different homogenization treatments, to achieve materials with different microchemistry states in terms of constituents, levels of Mn in solid solution (potential for concurrent precipitation) and dispersoid densities, followed by cold rolling and back-annealing. Characterization of the microchemistry state after homogenization and the evolution in dispersoid precipitation and its effects on the softening behavior after deformation has been performed. It is demonstrated that variations in microchemistry may have dramatic effects on the softening kinetics and the final grain structures, where both pre-existing fine and dense dispersoids before back annealing as well as precipitation concurrent with recovery and recrystallization strongly retard kinetics and generally lead to a coarse grain structure, while conditions with no or limited concurrent precipitation softens much faster and generally results in an even, fine and equi-axed grain structure. The different softening behaviors have been discussed in terms of Zener drag effects derived from the dispersoid evolutions.
Recrystallization of ECAP-Processed AA4343 Aluminium Alloy Containing Large Second Phase Particles
Authors: Paul Henryk , Baudin Thierry , Brisset François , Tarasek Anna
Published: March 2013

The objective of this study was to determine the effect of ECAP-processing on the texture and the microstructure development of the deformed and recrystallized material. The commercial purity AA4343 aluminium alloy, containing very large second phase particles (SPP) of pure silicon, was deformed via route C up to 10 passes and then annealed. The samples were characterized by TEM and SEM equipped with high resolution EBSD. It was found that the microstructure of the deformed state in areas far from coarse SPP was very similar to that observed in pure aluminium. The orientations of the new grains were scattered but not random and only specific groups of orientations were observed.
Grain Refinement in Cast Ti-6Al-4V by Hydrogenation, Deformation and Recrystallisation
Authors: Vilane Velile , Knutsen Robert D.
Published: March 2013

Hydrogenation and hot forging (upsetting) of cast Ti-6Al-4V has been performed at 550°C-1000°C at a strain rate of 10s-1. Post-deformation annealing studies were performed to establish minimum recrystallisation temperatures for optimizing grain refinement. Hydrogenation at approximately 20at.% hydrogen is shown to reduce the peak flow stress by up to 35% and lower the deformation temperature and recrystallisation limits to 550°C and 800°C respectively without compromising ductility during hot forging. Decomposition of the recrystallised β-phase and subsequent dehydrogenation provides substantial grain refinement of the cast structure.
In Situ X-Ray Diffraction Study of Thermal Stability of Cu and Cu-Zr Samples Processed by ECAP
Authors: Kužel Radomír , Matěj Zdeněk , Janeček Miloš
Published: March 2013

X-ray diffraction (XRD) studies of ECAP (equal-channel angular pressing) materials were performed after annealing and by in-situ measurements in XRD high-temperature chamber for samples prepared by different number of passes and number of revolutions, respectively. Main attention was given to Cu and Cu-Zr samples. Significant dependence on number of passes was found for ECAP samples. In-situ measurements were focused not only on temperature dependence but also on time evolution of the diffraction line profiles. Evaluation in terms of dislocation densities, correlation and crystallite size and its distribution was performed by our own software MSTRUCT developed for total powder diffraction pattern fitting. Abnormal growth of some grains with annealing is well-known for copper and leads to the creation of bimodal microstructure. Therefore a special care must be given to the evaluation and a model of two Cu components (larger and smaller crystallites) was fitted to the data if an indication of some crystallite growth appears either in the XRD line profile shape or in two-dimensional diffraction patterns.
An Evaluation of FIB Cross-Sectioning Using a Cooling Stage for Metals and Alloys with Low Melting Point
Authors: Matsushima Hideki , Suzuki Toshiaki , Nokuo Takeshi
Published: March 2013

Functions of an observation and an analysis in electron microscope, such as scanning electron microscope (SEM) or transmission electron microscope (TEM) are indispensable to evaluate advanced materials. Therefore a specimen preparation technique, that is a front end of the electron microscopy, has become highly important, thus a choice of it affects a result of the evaluation. The authors was combined a cooling stage in FIB and applied it for evaluation of metals with low melting point. The electron microscopic evaluation of Lead solder, Indium, Tin and Bismuth, metals with low melting point, has been always discussed if the results represent the actual physics. Metals with low melting point are heat sensitive materials, so the comparison of cross-sectioning with room and low temperature, it can be said that low temperature cross-sectioning has less effect and keeps the actual physics of the sample. In this paper, some knowledge from comparisons of cross-sectioning with room and low temperature for metals with low melting point are reported.
Recrystallization and Grain Growth due to Annealing of an Ultrafine-Grained Al Alloy
Authors: Loucif Aicha , Figueiredo Roberto B. , Baudin Thierry , Brisset François , Langdon Terence
Published: March 2013

The evolution of the recrystallization microstructure at different temperatures and the related change in the microhardness were studied in an Al-6061 alloy after 2 turns of high-pressure torsion (HPT) by means of Vickers microhardness and EBSD analysis. The corresponding results show that HPT processing introduces a significant grain size refinement for the deformed state by comparison with the 150 µm grain size in the initial material. The microstructure after annealing at 200°C is relatively close to the as-processed one and the distribution of misorientation angles remains essentially unchanged. However, significant microstructural changes are produced with increasing annealing temperature and at the highest temperature (400°C) there is an abnormal grain growth. The variation of Vickers microhardness (Hv) after the different annealing treatments show a gradual decrease when the temperature increases.
Development of Boundary Misorientations During Grain Growth in Silicon Steels
Authors: Hutchinson Bevis , Lindell David , Nave Mark , Rollett Anthony D.
Published: March 2013

Changes in grain size, texture and misorientation distributions have been monitored during extensive normal grain growth in 3%Si steels. The boundary misorientation distributions deviate significantly from the Mackenzie relationship. Comparisons of correlated and uncorrelated distributions show large excesses of low angle boundaries. However, these are not a result of low energy boundaries being favoured during grain growth since the deviation diminishes as growth proceeds. The effect originates in the nucleation of grains in colonies of similar orientation during primary recrystallisation. A slight tendency for promotion of 60º boundaries may indicate some preference for the retention of lower energy twin boundaries during grain growth in silicon steel.
Abnormal Grain Growth in Nanocrystalline Materials
Authors: Dake Jules M. , Krill III Carl E.
Published: March 2013

Much attention has been generated by nanocrystalline materials and their promise of enhanced properties. However, this class of materials suffers from an inherent instability with respect to thermally induced grain growth. Substantial microstructural coarsening is frequently observed in elemental samples even under ambient conditions, and more often than not, the mode of grain growth in such specimens is abnormal. Although deliberately adding an atomic species that segregates to the grain boundaries has been shown to stabilize the microstructure of nanomaterials to high fractions of the melting point, once grain growth commences, it generally proceeds in a highly abnormal manner in these samples, as well. In the case of Fe-based nanocrystalline alloys, abnormal growth appears to be intimately tied to the alpha-to-gamma phase transformation just above 900°C. For Ni-based segregation-stabilized specimens, however, there is no such allotropic transformation; nevertheless, the microstructure after growth manifests the same telltale signs of abnormality.
Strain Induced Abnormal Grain Growth in Nickel Base Superalloys
Authors: Bozzolo Nathalie , Agnoli Andrea , Souaï Nadia , Bernacki Marc , Logé Roland E.
Published: March 2013

Under certain circumstances abnormal grain growth occurs in Nickel base superalloys during thermomechanical forming. Second phase particles are involved in the phenomenon, since they obviously do not hinder the motion of some boundaries, but the key parameter is here the stored energy difference between adjacent grains. It induces an additional driving force for grain boundary migration that may be large enough to overcome the Zener pinning pressure. In addition, the abnormal grains have a high density of twins, which is likely due to the increased growth rate.
Grain Coarsening Characteristics of Modern Nb Microalloyed Steels
Authors: Zhu Zhi Xiong , Kuzmikova Lenka , Li Hui Jun , Chen Liang , de Jong Bob , Barbaro Frank J.
Published: March 2013

Modern steelmaking technologies utilizing microalloyed steel designs have been responsible for enormous economic benefits for both the steelmaker and fabricator. What has not been acknowledged is the environmental benefit that high strength steels have produced in terms of reduced steel usage in major infrastructure projects. The judicial use of microalloying has the potential to further reduce total tonnage requirements while delivering enhanced operational performance and service life. Various projects around the world have begun to recognize these recent microalloying developments. This paper will present the grain coarsening behavior of the new generation of Nb bearing steels, which have been used in major international steel fabrication projects.
Texture Change during Grain Growth in Non-Oriented Electrical Steel
Authors: Arita Yoshihiro , Ushigami Yoshiyuki , Murakami Kenichi , Ushioda Kohsaku
Published: March 2013

Texture change during grain growth in Fe-3%Si non-oriented electrical steel was investigated. Cold rolled steel, 0.35mm in thickness, was annealed and recrystallized as an initial structure. Normal grain growth and abnormal grain growth occurred by additional annealing. {111} was dominant in the initial texture. However {100} component, which was not in majority in the initial structure, became stronger after normal grain growth. It was revealed that an average grain size of {100} in the initial structure was bigger than those of other components by analysis of the EBSD data,. Therefore, it is concluded that {100} strengthened after normal grain growth due to its size advantage. On the other hand, {111} components became more stronger after abnormal grain growth. It is inferred that another mechanism of the texture change worked in abnormal grain growth.
Thermal Stability of Nanocrystalline Grain Size in Ternary Fe-Base Alloys
Authors: Koch Carl C. , Scattergood Ronald O. , Kotan Hasan , Saber Mostafa
Published: March 2013

We report recent research in our laboratory on the thermal stabilization of nanocrystalline binary alloys with ternary additions. Fe-Cr and Fe-Ni alloys with the ternary addition of Zr are studied. The thermal stability of these nanocrystalline alloys, prepared by mechanical alloying of powders, is studied by XRD, TEM and hardness as a function of annealing temperature. The relative importance of thermodynamic or kinetic stabilization in various temperature ranges is discussed for the different alloys. In agreement with our recent model for thermodynamic stabilization, it is found that Zr solute additions are more effective in stabilizing the nanocrystalline grain size in the Fe-Cr than in the Fe-Ni system.
Self-Similarity as a Feature of Nanocrystalline Grain Growth
Authors: Zöllner Dana , Streitenberger Peter
Published: March 2013

In the present work it is revealed by modified Potts model simulations and theoretical considerations that self-similarity is a feature of junction controlled grain growth as it can be found in nanocrystalline materials. To this aim the influence of the grain junctions – boundary faces, triple lines and quadruple points – on grain growth is analyzed by attributing each type of junction an own specific energy and mobility yielding nine types of growth kinetics, each characterized by a self-similar scaling form of the growth law and a corresponding self-similar grain size distribution.
Importance of Local Structural Variations on Recrystallization
Authors: Jensen Dorte Juul , Lin Feng Xiang , Zhang Yu Bin , Zhang Yong Hao
Published: March 2013

Effects of local variations in the deformation microstructure on subsequent recrystallization are discussed and illustrated by three examples. The three examples consider local variations on different length scales and are: 1. Effects of local variations in the deformation microstructure on the formation of protrusions on migrating boundaries. 2. Effects of an inhomogeneous spatial distribution of second phase particles on growth. 3. Effects of stored energy and orientation variations on recrystallization kinetics.
Effect of the Energy of Triple-Lines on 3D Grain Growth
Authors: Barrales-Mora L.A. , Shvindlerman Lasar S. , Gottstein Günter
Published: March 2013

The effect of the triple line energy on grain growth was studied by means of computer simulations with a network model. The results showed that the driving force stemming from the triple lines can influence significantly the evolution of grain growth.
Role of Mo on Static Recrystallization Kinetics in Coarse Grained Nb Microalloyed Steels
Authors: Pereda Beatriz , López Beatriz , Rodriguez-Ibabe J.M.
Published: March 2013

Thin slab direct rolling (TSDR) technology has some important metallurgical differences compared to conventional routes. One of these differences deals with the combination of coarse as-cast austenite grains and the possibility of limited solubility of microalloyed addition at the entry of the rolling mill. The industrial tendency of increasing the strength and toughness of steel grades produced by TSDR route requires increased amounts of Nb addition to achieve a proper austenite conditioning prior to transformation. Nevertheless, an increase in the Nb content rises the risk of premature Nb(C,N) precipitation during early rolling stages. In order to avoid this, one possibility is to add Mo and limit the amount of Nb. This study analyzes the influence of different Mo contents on static recrystallization of Nb microalloyed steels. The analysis includes the evaluation of the incidence of the combined effect of Nb and Mo solute drag retardation in both heterogeneous recrystallization evolution and grain size distribution for the case of initial coarse austenite grain sizes. To do that, partially recrystallized microstructures have been analyzed and microstructural parameters of interest quantified.
Crystallography of Natural and Synthetic Gold Alloy Microstructures
Authors: Halfpenny Angela , Hough Robert , Nugus Michael
Published: March 2013

To improve our understanding of the mechanisms of gold deposition, a comparison was made of the microstructures of a natural gold sample with a synthetic gold foil of similar alloy composition (approximately Au 90%, Ag 10%). The aim was to identify any similarities between the samples that could help increase our knowledge of how the natural gold microstructures formed and were modified post-mineralisation. The samples were analysed using electron backscatter diffraction to map their microstructure, with the synthetic gold foil then heated to and mapped at 400°C, 500°C, 600°C and 700°C. Both the natural and synthetic sample exhibited a dominance of ∑3 twin boundaries, but these were much less abundant in the synthetic sample prior to heating. The natural sample is dominated by coarse grains exhibiting lattice distortion and low angle grain boundaries, which more closely resemble the synthetic gold foil microstructure after recrystallisation has taken place, than the initial microstructure, implying that the grains have had time to grow. Performing experiments such as these allows direct comparison of gold microstructures where the formation conditions are known and the controlling mechanisms can be determined. This will improve our understanding of the important mechanisms behind gold deposition.
Role of Recrystallized Grains on the Environment-Assisted Cracking of Aluminium-Alloy
Authors: Kannan M. Bobby
Published: March 2013

In this study, the role of recystrallized grains on the environment-assisted cracking (EAC) susceptibility of a high strength aluminium alloy (Al-Zn-Mg-Cu) was examined using slow strain rate testing (SSRT) and U-bend test methods in chloride-containing solution. Experimental results suggest that the recrystallized grains in the peak-aged alloy are more prone to EAC. However, by altering the morphology and chemistry of the grain boundary precipitates of the recrystallized grains by overaging heat treatment, the alloy susceptibility to EAC reduced significantly.
Texture Formation in AA5182 Aluminum Alloy by Hot Extrusion
Authors: Okayasu Kazuto , Fukutomi Hiroshi
Published: March 2013

The behavior of texture formation in AA5182 aluminum alloy is investigated by hot extrusion tests under equivalent strain rates and temperatures ranging from 5.0×10-4 s-1 to5.0×10-2s-1 and from 723K to 823K, respectively. After the deformation, {001} (extrusion plane) and {111} double fiber texture is formed in all the deformation conditions. {001} texture develops after the deformation at 823K under equivalent strain rate of 5.0×10-3s-1 up to an extrusion ratio of 2.8. The size of {001} grains is larger than the mean grain size, suggesting that the {001} texture formation is attributed to grain boundary migration. Weakening of {001} texture is confirmed in the annealed section of the specimen.
Microstructure Development in Single and Double-Pass Friction Stir Processing of Aluminium
Authors: Yadav Devinder , Bauri Ranjit
Published: March 2013

Single pass and double-pass friction stir processing was carried out on commercially pure aluminium at a rotation speed of 640 rpm and traverse speed of 150 mm/min and a detailed electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) analysis was carried out to understand the microstructure developed. The grain size was refined substantially after the first pass whereas there was no significant change in the grain size after the second pass. This indicates that the final grain size after friction stir processing does not depend on the starting grain size. The equiaxed fine grains were formed by dynamic recrystallization process as revealed by EBSD analysis. TEM observations showed banded contrast across the grain boundaries indicating grain boundaries to be in equilibrium. Free dislocations observed inside grains after the first pass were well arranged into subgrain boundaries after the second pass. EBSD also revealed some variation in microstructural features such as grain size, texture index, grain orientation spread and grain average misorientation across the surface and also in the cross section of the stir zone both after single and double pass.
Effect of Fine Grain on Mechanical Properties of A6N01 Alloy
Authors: Kusuhara Hiroaki , Noguchi Munetoshi , Noda Masafumi , Mori Hisashi , Funami Kunio
Published: March 2013

The good formability and corrosion resistance of 6N01 Al alloy allow it to be utilized in high-speed train systems, and weight reduction of railway vehicles is possible by improving the strength of this alloy. This study examined the effect of the fine-grained structure on the mechanical properties of the alloy formed by a combination of heat treatment and severe plastic deformation such as forging and rolling. The role of the fine-grained structure in determining the plastic formability was also investigated. The 0.2% proof stress and tensile strength of the heat-treated and multi-axial alternative forging (MAF) processed materials were both greater than 300 MPa. Subsequent cold rolling of these alloys increased both the 0.2% proof stress and tensile strength to over 450 MPa with a grain size of less than 1 μm. The fine-grained structure was confirmed to be effective in improving the strength of the 6N01 Al alloy.
Dynamic Softening of Flow Stress during Dynamic Ferrite Transformation
Authors: Park Nokeun , Khamsuk Sunisa , Shibata Akinobu , Tsuji Nobuhiro
Published: March 2013

This study using a 6Ni-0.1C steel confirmed the relationship between the change in a fraction of dynamically transformed ferrite and the dynamic softening in stress-strain curve during dynamic transformation above ortho-equilibrium austenite-to-ferrite transformation temperature. Dynamic softening in stress-strain curve was well-fitted with a form of Avrami equation as a function of strain, and it corresponded with the change in fraction of ferrite. The slope of work-hardening rate was increased due to the additional softening phenomenon, i.e. dynamic transformation, to dynamic recovery of austenite. Dynamic softening of austenite, which has been considered as a typical evidence of dynamic recrystallization, could be interpreted as a response of dynamic transformation to ferrite.
Recrystallization of BCC Metals: Distribution of Strain Hardening and Texture Formation
Authors: Perlovich Yuriy , Isaenkova Margarita , Krymskaya Olga
Published: March 2013

Data are presented on the x-ray line broadening distribution over the texture of cold-rolled Nb and Mo sheets. The method of generalized X-ray pole figures, which combine texture measurements with X-ray line profile analysis, is employed. The X-ray line broadening is considered as an indicator of residual deformation effects. It was revealed that these effects in cold-rolled BCC metals rise as the grain orientation shifts away from texture maxima towards texture minima. The intensity of X-ray reflections change during annealing at 200 – 500C and this change correlates with the line broadening. The recrystallization texture of BCC metals is dominated by orientations deflected from the peak maxima by 25 – 30 deg. These orientations in the deformed structure have relatively high stored energy. Their volume fraction is sufficient for them to be able to consume most of the deformed matrix.
An Overview of the Effect of Nb in Strengthening Castrip® Steel
Authors: Shrestha Sachin L. , Zhu Chen , Proust Gwénaëlle , Barbaro Frank , Killmore Chris R. , Carpenter Kristin , Kaul Harold , Xie Kelvin Y. , Ringer Simon P. , Cairney Julie M.
Published: March 2013

Here we review research in which Vickers hardness tests, optical microscopy, electron backscatter diffraction, and atom probe tomography were used to understand the strengthening effects that can be found with Nb in CASTRIP® steels during thermo-mechanical processing and ageing. Nb addition favours the grain refinement of ferrite by inhibiting the austenite recrystallization when hot rolled and provides a strong cluster-hardening effect during ageing.
Evolution of Heterogeneous Deformation Structure and Recrystallization Texture of Steel
Authors: Ushioda Kohsaku , Nakanishi Sae , Morikawa Tatsuya , Higashida Kenji , Suwa Yoshihiro , Murakami Kenichi
Published: March 2013

Heterogeneous deformation during rolling is a crucial issue for elucidating recrystallization behavior. The progress thus far in our understanding of heterogeneity has been reviewed focusing on grain boundary and shear band. A statistical study on heterogeneous deformation structure using EBSD revealed that heterogeneity along the grain boundary can be classified into three types: 1) relatively flat boundary, 2) irregularly serrated boundary, and 3) boundary associated with fine grains. The fine grains in type 3 seem to be dynamically recovered as a cold-rolled state. Shear band formation is considered to be caused by plastic instability that is accelerated, for instance, by dynamic strain aging. A shear band is revealed to have a feature of recovered fine cells with Goss orientation already embedded in the shear band. The application of the phase-field method is exploited to predict recrystallization behavior and texture evolution during annealing based on the subgrain growth model. In simulation, a bulging mechanism seems to be dominant. Thus, a more rigorous description of the heterogeneous deformation structure is needed in the future
Microstructure Evolution and Softening Processes in Hot Deformed Austenitic and Duplex Stainless Steels
Authors: Cizek Pavel
Published: March 2013

The microstructure evolution and softening processes occurring in 22Cr-19Ni-3Mo austenitic and 21Cr-10Ni-3Mo duplex stainless steels deformed in torsion at 900 and 1200 °C were studied in the present work. Austenite was observed to soften in both steels via dynamic recovery (DRV) and dynamic recrystallisation (DRX) for the low and high deformation temperatures, respectively. At 900 °C, an “organised”, self-screening austenite deformation substructure largely comprising microbands, locally accompanied by micro-shear bands, was formed. By contrast, a “random”, accommodating austenite deformation substructure composed of equiaxed subgrains formed at 1200 °C. In the single-phase steel, DRX of austenite largely occurred through strain-induced grain boundary migration accompanied by (multiple) twinning. In the duplex steel, this softening mechanism was complemented by the formation of DRX grains through subgrain growth in the austenite/ferrite interface regions and by large-scale subgrain coalescence. At 900 °C, the duplex steel displayed limited stress-assisted phase transformations between austenite and ferrite, characterised by the dissolution of the primary austenite, formation of Widmanstätten secondary austenite and gradual globularisation of the transformed regions with strain. The softening process within ferrite was classified as “extended DRV”, characterised by a continuous increase in misorientations across the sub-boundaries with strain, for both deformation temperatures.
A Comparison of Grain Boundary Character Distributions between Grain Boundary Engineered Austenitic Stainless Steel and Pb-Ca Based Alloy
Authors: Wang Wei Guo , Fang Xiao Ying , Guo Hong
Published: March 2013

Though there developed same concentrations of special grain boundaries (SBs) in grain boundary engineered (GBE) austenitic stainless steel (304 stainless steel) and a Pb-Ca based alloy, the makeup of SBs, size distribution of clusters of grains with ∑3n (n=1,2,3) orientation relationships (∑3n CG), and grain orientations (textures) are quite different between the two specimens, suggesting there have two different mechanisms separately governing the evolution of grain boundary character distributions (GBCDs) in the two types of materials during GBE processing.
IL7Rα Contributes to Experimental Autoimmune Encephalomyelitis through Altered T Cell Responses and Nonhematopoietic Cell Lineages
Authors: Ashbaugh Jessica J. , Brambilla Roberta , Karmally Shaffiat A. , Cabello Cecilia , Malek Thomas R. , Bethea John R.
Published: March 2013

A mutation in the IL7Rα locus has been identified as a risk factor for multiple sclerosis (MS), a neurodegenerative autoimmune disease characterized by inflammation, demyelination, and axonal damage. IL7Rα has well documented roles in lymphocyte development and homeostasis, but its involvement in disease is largely understudied. In this study, we use the experimental autoimmune encephalomyelitis (EAE) model of MS to show that a less severe form of the disease results when IL7Rα expression is largely restricted to thymic tissue in IL7RTgIL7R−/− mice. Compared with wild-type (WT) mice, IL7RTgIL7R−/− mice exhibited reduced paralysis and myelin damage that correlated with dampened effector responses, namely decreased TNF production. Furthermore, treatment of diseased WT mice with neutralizing anti-IL7Rα Ab also resulted in significant improvement of EAE. In addition, chimeric mice were generated by bone marrow transplant to limit expression of IL7Rα to cells of either hematopoietic or nonhematopoietic origin. Mice lacking IL7Rα only on hematopoietic cells develop severe EAE, suggesting that IL7Rα expression in the nonhematopoietic compartment contributes to disease. Moreover, novel IL7Rα expression was identified on astrocytes and oligodendrocytes endogenous to the CNS. Chimeric mice that lack IL7Rα only on nonhematopoietic cells also develop severe EAE, which further supports the role of IL7Rα in T cell effector function. Conversely, mice that lack IL7Rα throughout both compartments are dramatically protected from disease. Taken together, these data indicate that multiple cell types use IL7Rα signaling in the development of EAE, and inhibition of this pathway should be considered as a new therapeutic avenue for MS.
The impact of four harvesting techniques on the cell viability and osteogenic behaviour of cells in autogenous bone grafts: A critical appraisal of an experimental study
Authors: Van Zyl Andre W. , Hartshorne Johan , Carrasco-Labra Alonso
Published: March 2013

The investigators tested the null hypothesis that there would be no differences between the different bone harvesting techniques with regard to cell viability, cell activity and osteogenic potential of grafted cells. Bone grafts were harvested from the mandibles of 12 miniature pigs using four different harvesting techniques: bone milling, bone scraping, bone drilling (bone slurry) and piezosurgery. Cell viability was determined according to an immunoassay of released signalling molecules and gene expression that affect bone formation and resorption. The osteogenic activity of conditioned graft-sampled media was assessed in a bioassay using isolated bone cells. Cells in autogenous bone grafts obtained by using a bone mill and a bone scraper showed a higher viability and a stronger osteogenic potential than those from piezosurgery and bone drilling (slurry). This study contributed towards the understanding of the impact of harvesting techniques on the viability and osteogenic behaviour of grafted cells.