bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystallization Kinetics of MgO–Al2O3–SiO2 Transparent Glass–Ceramics
Authors: Cheng Jin Shu , Wang Jing , Tang Li Ying , Deng Zhen Lu
Published: April 2012

The non-isothermal crystallization kinetics of the MgO–Al2O3–SiO2 (MAS) glasses were analyzed with the Kissinger equation and the Augis-Bennett equation by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that two crystal phases of spinel (MgAl2O4) and SiO2 were generated sequentially in the heat treatment process. When the spinel was the only crystal phase, the MAS glass-ceramic was transparent. For glass A (containing one type alkali metal Na2O), the corresponding activation energy was Ep1(A)=325.27kJ/mol, Ep2(A)=364.99kJ/mol; for glass B (containing Na2O and K2O) , the activation energy is Ep1(B)=233.79kJ/mol, Ep2(B)=273.85kJ /mol. The average crystallization index for spinel crystal phase was nA1=1.99, nB1=2.58, By adding K+, which suggested that the spinel crystal phase precipitation have the trend to change from two-dimensional pattern to bulk crystallization.
Effect of Polyvinyl Pyrrolidone Molecular Weight on the Silver Morphology Synthesized by N, N-Dimethylformamide Reduction
Authors: Zhu Xuan Min , Zhao Xiu Jian , Ning Zhi Yong , Sui Xiao Tao
Published: April 2012

Nanosized silver (Ag) was synthesized by reducing high concentration AgNO3 in N, N-dimethylformamide (DMF), in the presence of stabilizer polyvinyl pyrrolidone (PVP). PVP of two different molecular weights (MW=40000, 1300000) at the reaction temperature of 80°C and 100°C were tested for the effect on the formation of diverse silver nanoparticles. Our results indicated that the PVP with different molecular weights plays different role in the controlling of the Ag nanostructure owing to the PVP molecular selective adsorption on different crystal facets, thus affecting the growth rate of different facets of Ag nanoparticles. When all the other conditions kept the same and the temperature of 100°C, if PVP (Mw=40,000) was used, only a small amount of Ag decahedra were found. However, when the PVP with larger molecular weight such as PVP K88 (Mw=1300, 000), a large quantity of the triangular nanoprisms existed in the final solution in spite of the minority of quasi-sphere. The growth process and causation of different silver morphology with two distinct PVP have been briefly discussed.
Improvement on the Crack Resistance Property of Semi-Flexible Pavement by Cement-Emulsified Asphalt Mortar
Authors: Huang Chong , Liu Jia Ping , Hong Jin Xiang , Liu Zhi Fei
Published: April 2012

Semi-flexible pavement (SFP) has some excellent characteristic such as high carrying capacity, good wearing resistance, water stability and durability. However, the SFP appears low temperature crack and fatigue cracking seriously because there are large differences in the interfacial bonding property and the elastic modules between its two major parts: Lag gap asphalt mixture (LGAM) and cement mortar. All of these are caused by the large stiffness of cement mortar. In order to improve the crack resistance property of SFP, six kinds of cement-emulsified asphalt mortars (CEAM) were developed to enhance the adhesive property and reduce the elastic modules. The cement-emulsified asphalt mortar semi-flexible pavement material (CEAMSFP) was obtained by using this kind of CEAM. In the CEAM and the CEAMSFP, six emulsified asphalt-to-cement (A/C) ratios were considered in the study: 0, 0.1, 0.2, 0.3, 0.4 and 0.5 by weight of emulsified asphalt. The results indicated that the increasing of the A/C ratio improved the bonding interface and the flexible of the CEAM. The increasing of the A/C ratio improved the low temperature resistance and fatigue life of the CEAMSFP. It was also shown that the A/C ratio of 0.3 was found to be the optimum ratio that achieved a balance in performance and the value of the pavement. In this condition, the adhesion level between LGAM and cement grout reached 5，the elastic modules of mortar decreased by 62.5% and the fatigue life of SFP increased by 43.6%.
Microstructure and Luminescent Properties of the YAG: Ce Phosphor-Doped Glass of the P2O5-ZnO-SiO2 System
Authors: Hong Li , Ning Hua , Qing Ye
Published: April 2012

Lminescent glass is widely used in building, energy saving, emergency lighting and art crafts; The energy consumption for global illumination is rising year by year, and the energy consumption has become a global problem; the research of luminescent glass is important for the developing of the energy-saving light. In this paper, the glass of the P2O5-ZnO-SiO2 system was used as matrix material, the matrix material was doped with yttrium aluminum garnet crystals containing Ce (YAG:Ce phosphors) and then were sintered for the preparation of the luminescent glass. Using X-ray diffraction and fluorescence spectrometer, the effects of the doping quantity, sintering temperature and sintering time on luminescent properties were studied. The results show that, for the P2O5-ZnO-SiO2 glass, excitation at 340 nm and 468 nm, produced emission at 544 nm; Doping quantity, sintering temperature and sintering time affect intensity of emission peak, but do not affect the position of emission peak.
Preparation and Analysis of Doped TiO2 in the Bi2O3-SiO2-ZnO-B2O3 Low-Melting Sealing Glasses
Authors: Gu Qi Bin , Ni Jia Miao
Published: April 2012

In this paper, optical, the chemistry stability, and glass transformation, softening temperature were studied on Bi2O3-SiO2-ZnO-B2O3 system glass doped with 2wt.%、4wt.%、6wt.% and 8wt.%TiO2. The results showed that glass surface has no stripes and defects with transmittance between 20%-50%. Moreover, with the increasing of Ti content, the results of the experiments indicated that the metal oxides TiO2 could enhance the glass chemical stability most clearly, and regulate the glass transformation temperature.
Investigation on Recycled Cement Based on Waste Concrete
Authors: Lin Zong Shou , Chong Yan
Published: April 2012

Adding part of granulated blast furnace slag(GBFS), steel salg(SS) , Desulfurization gypsum(DG), we can use Waste Cencrete（WC）as the main raw materials to directly produce uncalcined cement by grinding.With mix proportion 40%~50% of WC and curing in water, the 3d compressive strength of the cement can reach 10MPa.,the 28d compressive strength of the cement can reach 20~40MPa. XRD and SEM analysis show that, the hydration products of the cement are ettringite and C-S-H gel. Parts of WC involves in the hydration reaction, residual WC is wrapped by the hydration product as aggregate filler.
Relationship between Structure and Performance of Polycarboxylate Superplasticizer
Authors: Wang Zi Ming , Lu Zi Chen , Lu Fang , Li Hui Qun
Published: April 2012

The structure of the polycarboxylate superplasticizer (PCE) and the relationship between the structure and the performance of PCE were summarized and analyzed. Based on these results achieved so far, the consensus and the unified opinions were presented while the ambiguous and contradictory points were compared and discussed. Furthermore, the different effect on performance caused by different structure such as side chain length, degree of polymerization, side chain density, functional group were discussed systematically. Finally the existing problems and the measures to be taken in the future were proposed
Study on the Frost Resistance of Artificial Aggregates Recycled Concrete
Authors: Wang Jin Bang , Zhou Zong Hui
Published: April 2012

The recycled concrete was prepared by using the high-strength artificial aggregates. This kind of concrete can be completely regenerated to be cement, and the recycling utilization of the concrete can also be truly realized. The frost resistance and influencing factors of the recycled concrete were studied. The results show that the mechanical performance and frost resistance of artificial aggregates recycled concrete are better than those of the ordinary concrete under the same water/cement ratio condition. When the water/cement ratio is 0.40, the relative dynamic elastic modulus, weight loss and frost durability factor of the recycled concrete are 98.7%, 0.5% and 65.8 after 200 times freeze-thaw cycles. When the fly ash and silica fume were added into the recycled concrete, the frost resistance can be improved. The optimal amounts of fly ash and silica fume are 30% and 15% of cement by weight, respectively. The recycled concrete was prepared with the optimal fly ash and silica fume content, respectively. After 200 times freeze-thaw cycles, the relative dynamic elastic modulus of the recycled concrete are 99.1% and 99.2%, and the weight losses of the recycled concrete are 0.4% and 0.3%, and antifreeze durability coefficient of the recycled concrete are 66.07 and 66.13. Therefore, the recycled concrete with silica fume has better frost resistance performance than that with fly ash as admixture.
Directed Growth of Ferrite in Austenite and Kurdjumov-Sachs Orientation Relationship
Authors: Lee Dong Nyung , Han Heung Nam
Published: April 2012

The solid phase transformation of a metastable phase into a stable phase needs the activation energy. The energy is usually supplied in the form of thermal energy. When the nucleation takes place, the strain energy may develop in the metastable matrix and the stable nucleus. The strain energy can result from differences in density of the nucleus and matrix and the lattice mismatch between the nucleus and matrix. The stable-metastable interface region has the highest strain-energy density in the maximum Youngs modulus direction of the stable phase. Accordingly, the growth rate of the stable phase is the highest in its highest Youngs modulus directions. As the transformation temperature decreases, the strain energy contribution increases and the growth rate anisotropy is likely to increase. When austenite transforms into ferrite at low temperatures, the directed growth of ferrite is observed as forms of Widmanstätten ferrite plates and acicular ferrite plates. The maximum growth direction of ferrite is along the maximum Youngs modulus direction of ferrite, <111>α, and the broad interfaces are parallel to the maximum growth direction and formed so that they minimizes the shear strain energy in the interface layer. The directed growth results in the Kurdjumov-Sachs orientation relationship between austenite and ferrite, <111>α//<110>γand {110}α//{111}γ.
Origin of the {h 1 1 }<1/h,1,2> Fiber in Single Phase Ferrite Steels
Authors: Gobernado Patricia , Petrov Roumen H. , Moerman Jaap , Barbatti Carla , Kestens Leo
Published: April 2012

In the present work, the oriented nucleation origin of the recrystallized {h11}<1/h,1,2> fibre is characterized. Aiming to investigate the substructural evolution of <110>//RD fibre grains and {001}<110> grains in particular, a detailed microstructure and texture analysis is performed by high resolution orientation scanning microscopy on a cross-rolled sample. The reason to work with cross-rolled material is the increased incidence of rotated cube orientations after cross rolling. The present data have revealed the presence in the deformed substructure of a crystallite volume that has rotated towards the {311}<136> component in the interior of <110>//RD fibre grains as a result of a grain fragmentation process. Preliminary simulations of the deformation texture suggested that the observed orientation fragmentation might be produced by strain localizations of a shear band nature.
Dynamic Recrystallisation during Isothermal Hot Deformation in a Titanium Modified Austenitic Stainless Steel
Authors: Mandal Sumantra , Bhaduri A.K. , Raj Baldev , Sarma V. Subramanya
Published: April 2012

The paper discusses the microstructural evolution during dynamic recrystallisation (DRX) of a titanium-modified austenitic stainless steel (alloy D9). Isothermal hot compression tests were conducted in a Gleeble thermo-mechanical simulator in the temperature range 1173-1373K to various strains at a constant strain rate of 0.1 and 1 s-1. The extent of DRX increased with increase in strain and temperature. Nucleation of new DRX grains was found to occur by bulging of parent grain boundary. A continuous sub-grain rotation around the original grain boundaries, which would lead to the formation of DRX nucleus in sub-grain structures, could not be confirmed from the present study. Fractions of Σ3 boundaries increased almost linearly with increase in area fraction of DRX. The generation of this Σ3 boundary was accounted for in the formation of annealing twins during DRX. The possible role of annealing twins on DRX in alloy D9 is also discussed.
New Recrystallisation Behaviour Seen in Magnesium Alloy Elektron 675
Authors: Randman D. , Corteen J. , Rainforth W.M. , Wynne B.P. , Davis B.
Published: April 2012

There has recently been renewed interest in magnesium alloys from both the automotive and aerospace industries. Due to the low density (approximately 35% lower than aluminium) and high specific strength, these alloys can introduce significant weight savings, and consequently fuel savings, to both vehicles and aircraft. Elektron™ 675 is a new alloy based on the magnesium-yttrium-gadolinium ternary system, developed by Magnesium Elektron Ltd. for wrought applications. Elektron™ 675 has superior mechanical properties relative to the current commercially available wrought alloys AZ31B, WE43, and ZK60.
Substructure and Texture Characteristics of the Deformed Matrix and Dynamically Recrystallized Grains in a Ni-30%Fe Austenitic Alloy
Authors: Cizek Pavel , Beladi Hossein , Hodgson Peter D.
Published: April 2012

The substructure and crystallographic texture characteristics of both the deformed matrix and dynamically recrystallized (DRX) grains were investigated in a Ni-30%Fe austenitic model alloy subjected to hot torsion. Deformation was performed at a temperature of 1000°C using strain rates of 1, 0.1 and 0.01 s-1, which produced a range of DRX grain sizes. Electron back-scattered diffraction and transmission electron microscopy were employed in the investigation. Both the deformed matrix and DRX grains revealed the texture components expected for simple shear deformation by crystallographic slip. The texture of DRX grains was dominated by low Taylor factor components as a result of their lower consumption rate during growth of these grains. There was a marked difference in the substructure characteristics between the deformed matrix and DRX grains regardless of the grain size and orientation. The deformed matrix substructure was largely characterized by organized, banded subgrain arrangements with alternating misorientations. By contrast, the substructure of DRX grains was generally more random in character and displayed complex, more equiaxed subgrain/cell arrangements characterized by local accumulation of misorientations. Based on the experimental observations, a mechanism of the distinct substructure development within DRX grains has been proposed.
Understanding Grain Boundary Junctions: Effect of the Grain Size on Microstructure Evolution
Authors: Barrales Mora Luis A. , Shvindlerman Lasar S. , Gottstein Günter
Published: April 2012

In a previous work [ we introduced the geometry of a granular system that allowed the study of the effect of a finite mobility of the quadruple and triple junctions on grain boundary migration. One of the most important conclusions of this work was that the triple junctions drag more effectively the motion of the grain boundaries than the quadruple junctions. Nevertheless, this conclusion was drawn without consideration of the grain size. For this reason, this conclusion might be contradictory with our understanding of the grain boundary junctions because while the effect of the triple lines is inverse linear with the grain size that of the quadruple junctions is proportional to the inverse square of the grain size and thus, quadruple junctions are expected to drag more effectively, at least, for very small grain sizes. In the present investigation, we studied comprehensively the effect of grain size on the evolution of the granular system under the assumption of a finite mobility of the boundary junctions. For this purpose, several network model simulations were carried out for different grain sizes ranging from nanoto micrometers using a fully periodic grain arrangement. The results seem to corroborate that the triple junctions drag more effectively the motion of the grain boundaries, however, for very low junction mobility and grain sizes the effect appears to be indistinguishable. It was also observed that for very low quadruple junction mobility the geometry of the granular system undergoes a severe transformation which results in the unfulfillment of the equation derived in [.
A Different View on Dynamic Recrystallization
Authors: Gottstein Günter
Published: April 2012

A new approach to dynamic recrystallization (DRX) is introduced. It is based on the assumption that the critical conditions for DRX and the arrest of DRX grain boundaries are related to the development of mobile subboundaries. The theoretical predictions are compared to experimental results during incipient and steady-state DRX. The grain size sensitivity of the DRX grains establishes the desired link between deformation and DRX microstructure.
New Insights into the Dynamic and Metadynamic Recrystallization of Austenite
Authors: Hodgson Peter D. , Cizek Pavel , Beladi Hossein
Published: April 2012

The present work provides a summary of the recent findings obtained from the experimental investigation of the grain structure, crystallographic texture and dislocation substructure evolution in an austenitic Ni-30%Fe model alloy during dynamic recrystallization (DRX) and post-dynamic annealing. It has been found that the DRX texture characteristics become increasingly dominated by the low Taylor factor grains during DRX development, which presumably results from the preferred nucleation and lower consumption rates of these grains. The substructure of DRX grains is random in character and displays complex, hierarchical subgrain/cell arrangements characterized by accumulation of misorientations across significant distances. The stored energy within DRX grains appears to be principally consistent with the corresponding Taylor factor values. The changes observed within the fully dynamically recrystallized microstructure during post-dynamic annealing have provided a basis to suggest a novel mechanism of metadynamic softening for the current experimental conditions. It is proposed that the initial softening stage involves rapid growth of the dynamically formed nuclei and migration of the mobile boundaries. The sub-boundaries within DRX grains progressively disintegrate through dislocation climb and dislocation annihilation, which ultimately leads to the formation of dislocation-free grains, and the grain boundary migration gradually becomes slower. As a result, the DRX texture largely remains preserved throughout the annealing process.
Austenite Grain Growth Kinetics during Continuous Heating of a Microalloyed X-80 Linepipe Steel
Authors: Banerjee Kumkum , Perez Michel , Militzer Matthias
Published: April 2012

Non-isothermal austenite grain growth kinetics has been studied in a microalloyed linepipe steel with complex precipitates containing Ti, Nb and/or Mo. The goal of these experimental studies is to provide the basis for the development of a grain growth model to predict the austenite grain size evolution in the weld heat affected zone (HAZ). Detailed electron microscopic investigations of the as received steel proved the presence of Ti-rich, Nb-rich and Mo-rich precipitates. The steel was subjected to austenitizing heat treatments to selected peak temperatures of 950, 1150 and 1350 °C at heating rates of 10, 100 and 1000 °C/s, respectively. Thermal cycles have been found to have a strong effect on the austenite grain size. Austenite grain sizes increase with peak temperature and decreasing heating rate. However, the increase in heating rate from 100 to 1000 °C/s has a negligible effect on the austenite grain size. The observed austenite grain growth kinetics can be explained taking into account the potential dissolution of Nb-rich precipitates.
The Influence of Strain on Annealing Behaviour of Heavily Rolled Aluminium AA1050
Authors: Mishin O.V. , Jensen Dorte Juul , Hansen Niels
Published: April 2012

Deformation structures and annealing behaviour have been analysed in the centre layer of two AA1050 samples cold-rolled to von Mises strains of 3.6 and 6.4. During annealing at 270-300°C structural coarsening and discontinuous recrystallization occurred in both samples. In the coarsened microstructure, the fraction of high angle boundaries was slightly lower than that in the as-rolled conditions. Recrystallization textures of both samples contained significant fractions of the rolling texture components. The fraction of the retained rolling texture was however greater in the strain-6.4 sample. The {001}<310> and {110}<566> components were also pronounced in this sample. The size of recrystallized grains having orientations of the rolling texture was considerably smaller than the size of grains having other crystallographic orientations. This may be attributed to orientation pinning that hinders growth of grains with orientations of the rolling texture.
Strain Induced Inward Grain Growth during Recrystallisation in Steel Sheets with BCC Crystal Structure
Authors: Gautam Jai , Petrov Roumen H. , Leunis Elke , Kestens Leo
Published: April 2012

The present paper investigates the potential application of Strain Induced Boundary Migration mechanism on the two different types of surface textures developed after α-γ-α phase transformation annealing, one with preferred cube and Goss orientation at the surface and the other with random surface texture without preferred orientations. It has been demonstrated that these surface texture components grow in across the thickness of the sheet after an appropriate combinations of a critical amount of rolling reductions and an annealing treatment at the recrystallisation temperature.
Thermodynamic Stabilization of Grain Size in Nanocrystalline Metals
Authors: Koch Carl C. , Scattergood Ron O. , VanLeeuwen Brian K. , Darling Kristopher A.
Published: April 2012

This paper describes the stabilization of nanocrystalline grain sizes in Pd and Fe by the addition of Zr solute atoms. The grain size as a function of annealing temperature was measured by both x-ray diffraction (XRD) line broadening analysis and microscopy methods. The latter methods showed that the XRD grain size measurements for the samples annealed at the higher temperatures were not valid. It appears that thermodynamic stabilization may still be operative in the Fe-4at.% Zr alloy but not in the Pd-19at.% Zr alloy from the experimental results and calculations of the enthalpy of segregation.
Recrystallized Grain Size in Single Phase Materials
Authors: Wang Sheng Yu , Rollett Anthony D. , Holm Elizabeth A.
Published: April 2012

During large-strain plastic deformation, subgrain structures typically develop within the grains. At large enough equivalent strains above, say 0.5, recrystallization occurs via abnormal coarsening of the subgrain structure or abnormal (sub-) grain growth (AsGG). The fraction of subgrains that develop into new, recrystallized grains has been quantified as a function of texture spread (Grain Reference Orientation Deviation) using Monte Carlo simulation. When this fraction is combined with the known monotonic increase in mean misorientation with strain, the recrystallized grain size can be predicted as a function of von Mises strain. The prediction is in good agreement with experimental results drawn from the literature.
Recrystallization and Grain Growth in Ultra Fine Grained Materials Produced by High Pressure Torsion
Authors: Khorashadizadeh Anahita , Winning Myrjam , Zaefferer Stefan , Raabe Dierk
Published: April 2012

Investigations of the microstructure of materials processed via severe plastic deformation methods such as high pressure torsion (HPT) and their recrystallization behaviour is of great interest as they are capable of producing ultra fine grained material (UFD) with good mechanical properties.
The Formation of Fine-Grained Structure in S304H-Type Austenitic Stainless Steel during Hot-To-Warm Working
Authors: Tikhonova Marina , Dudko Valeriy , Belyakov Andrey , Kaibyshev Rustam
Published: April 2012

The dynamic process of grain evolution in a Super304H austenitic stainless steel was studied in compression tests. The tests were carried out to a strain of 0.7 at temperatures ranging from 700 to 1000°C and strain rate of 10-3s-1. In addition to single pass compression the multiple compressions with changing the loading direction in 90o and decreasing the temperature with step of 100°C from 1000 to 700°C in each pass were utilized to achieve large cumulative strains. Under multiple compression the values of flow stresses were lower than those at single-pass compressions under the same temperatures. The fraction of dynamically recrystallized grains decreased from 1.0 to almost zero with decreasing temperature in single-pass compressions. On the other hand, almost fully recrystallized structure developed under conditions of multiple compressions. The size of dynamically recrystallized grains decreased with decreasing the deformation temperature, approaching a submicrometer scale level at 700°C. The relationship between the deformation conditions and operating mechanisms of dynamic recrystallization is discussed in some details.
Modelling Discontinuous Dynamic Recrystallization Using a Physically-Based Model for Nucleation
Authors: Cram Darren G. , Zurob Hatem S. , Bréchet Yves J.M. , Hutchinson Christopher R.
Published: April 2012

A physically-based model for nucleation during discontinuous dynamic recrystallization (DDRX) has been developed and is coupled with polyphase plasticity and grain growth models to predict the macroscopic stress and grain size evolution during straining. The nucleation model is based on a recent description for static recrystallization and considers the dynamically evolving substructure size. Model predictions are compared with literature results on DDRX in pure Cu as a function of initial grain size, deformation temperature and strain-rate. The characteristic DRX features such as single to multiple peak stress transitions and convergence towards a steady-state stress and grain size are quantitatively reproduced by the model.
A 3D FIB Investigation of Dynamic Recrystallization in a Cu-Sn Bronze
Authors: Gholinia Ali , Brough Ian , Humphreys John F. , Bate Pete S.
Published: April 2012

A combination of electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques were used to obtain 3D EBSD data in an investigation of dynamic recrystallization in a Cu-2%Sn bronze alloy. The results of this investigation show the origin of the nucleation sites for dynamic recrystallization and also elucidates the orientation relationship of the recrystallized grains to the deformed, prior grains and between the dynamically recrystallized grains.
Microstructure, Texture and Recrystallisation Mechanisms of an Al-20%Sn Deformation Processed Metal-Metal Composite
Authors: Schouwenaars Rafael , Duran Hugo A. , Jacobo Víctor H. , Ortiz Armando
Published: April 2012

Al-Sn alloys for tribological applications are industrially important alloys which have attracted little attention over their history. Being cold rolled directly from thin cast slabs and consisting of two ductile phases, their processing and physical behaviour are distinct from classical Al-Alloys. During cold rolling, the coarse-grained, random texture of the slab is transformed into the classical rolling texture of a fine-grained Al-alloy, with elongated Al-grains delimited by thin Sn-ribbons. During annealing at 300°C, the interior of the Al-grains recrystallises rapidly while the liquid Sn-phase migrates toward Al-grain triple lines to form a reticular structure. A weak texture, dominated by Goss and P is produced. Grain growth within the original cold-rolled grains is fast, but once the recrystallised grain size reaches the length scale of the second-phase distribution, it slows down and both phases coarsen simultaneously, accompanied by a significant texture change.
Microstructure Instability during Particle and Solute Inhibited Grain Growth
Authors: Buccioni Massimiliano , Abbruzzese Giuseppe Carlo
Published: April 2012

Grain growth processes in real polycrystalline materials are mostly characterized by the presence of restraining forces, originating, among others, from second phase particles dispersion (Zener drag) or solute atoms segregating at the grain boundaries (solute drag). Both the restraining mechanisms were introduced in the framework of the statistical theory of grain growth, showing their peculiar effects on kinetics and on grain size distribution evolution [1,2,. The present work moves from the previous results and gives a further clarification of pseudo-steady state kinetics occurring under particular solute drag inhibition intensity and will discuss it in comparison with grain growth stagnation conditions produced by Zener drag. In case of second phase particle inhibiting grain growth, the normal case in real systems is the time and temperature dependence of the inhibition intensity due to the evolution of precipitates (e.g. Ostwald ripening. Such evolutions of inhibition, which typically drops with increasing temperature, can cause microstructure instabilities like abnormal grain growth or secondary recrystallization. It is thus introduced in the model a time-temperature depending inhibition drop, which influences both kinetics and grain size distribution evolution. Conditions for the onset of particular effects like abnormal grain growth are assessed and discussed.
Microstructural Modelling Applied to the Design and Control of the Steel Plate Rolling Process
Authors: Doell R. , Lee Joseph , Harvey A. , Steeper M.
Published: April 2012

Modern steel plate manufacture relies on the manipulation of recrystallisation and grain growth in order to obtain maximised and precise mechanical properties from low-alloyed feedstock. The models that describe this metallurgical process nowadays inform the design of the plant itself. They are also capable of application to the on-line control of rolling, as well as to several of the ancillary mill operations.
Recrystallization and Mechanical Behavior of High Mn and Low C Cold Rolled and Annealed Steel with TWIP Effect
Authors: Santos Dagoberto Brandao , Gonzalez Berenice Mendonça , Pereloma Elena V.
Published: April 2012

ncreasing demand for automotive vehicles with reduced weight, improved crashworthiness and passengers safety has steamed the research of new Twinning Induced Plasticity (TWIP) steels. In this work the effect of annealing between 400 and 900°C on the microstructure and mechanical properties of hot and cold rolled 0.06C-24Mn-3Al-2Si-1Ni (wt%) steel with TWIP effect was investigated. The results have shown that steel exhibits fast recrystallization kinetics with a low amount of recovery, which results in a high driving force for the former. Mechanical properties were determined using Vickers microhardness and tensile tests. Tensile strength of 670 MPa with 54% of total elongation, and strain hardening exponent of 0.57 were reached after annealing at 900°C.
Mechanisms of Dynamic Recrystallization in Coarse Columnar-Grained Cu-Sn-P Alloy
Authors: Miura Hiromi , Watanabe Masato , Shirai Takashi , Ishibashi Akihiko
Published: April 2012

Dynamic recrystallization (DRX) behavior in a coarse columnar-grained Cu-0.65Sn-0.025P and Cu-0.025P (mass%) alloys were systematically investigated by compression tests at temperatures between 1073 K and 1253 K and at true strain rates from 2 x 10-4s-1to 2 x 10-1s-1in vacuum. As a model sample, an orientation-controlled bicrystal having [0 1 twist 18oboundary was prepared and also hot deformed. Appearance of the peaks stress, where DRX onsets, was much delayed in Cu-Sn-P alloy compared with that in Cu-0.025P alloy. The onset of DRX was, therefore, obviously impeded by the small addition of Sn to Cu-P. While nucleation of new grains took place almost at random in Cu-Sn-P when strain rate was high enough, it tended to appear more preferentially at grain boundary with decreasing strain rate and with increasing temperature. The most of new grains were annealing twins formed behind the migrating grain boundary. Because grain boundary migration took place more extensively with increasing temperature and with decreasing strain rate, the preferential nucleation at grain boundary became more significant.
The Influence of Oxide Inclusion on Austenite Grain Size and Heat Affected Zone Toughness for Low Carbon Steels
Authors: Shu Wei , Wang Xue Min , Shang Cheng Jia , He Xin Lai
Published: April 2012

The low carbon steels were smelted with special oxide introduction technique and the HAZ properties has been studied with thermal simulation. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the mechanical properties after thermal simulation were also investigated. The influence of oxide inclusions on the austenite grain size was also studied. The results show that after the smelting the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. When the reheat temperature is below 1000, the size of austenite grain is the same for experimental steel and base steel. However, when the reheat temperature is over than 1100, the size of austenite grains in experimental steel is one third of that in base steels. After thermal simulation, with thet8/5increasing the toughness of HAZ decreased. The austnite grain size also increased. The microstructure is composed of intergranular ferrite and intragranular acicular ferrite. Therefore by introducing the fine oxide inclusion to the steel the austenite grain was refined and during the phase transformation the acicular ferrite formed at inclusions at first. These two factors are the main causes to improve the toughness of heat affected zone for steels produced by oxide metallurgy technique.
Towards a Phase Field Model of the Microstructural Evolution of Duplex Steel with Experimental Verification
Authors: Poulsen S.O. , Voorhees Peter W. , Lauridsen Erik M.
Published: April 2012

A phase field model to study the microstructural evolution of a polycrystalline dual-phase material with conserved phase fraction has been implemented, and 2D simulations have been performed. For 2D simulations, the model predicts the cubic growth well-known for diffusion-controlled systems. Some interphase boundaries are found to show a persistent non-constant curvature, which seems to be a feature of multi-phase materials. Finally, it is briefly outlined how this model is to be applied to investigate microstructural evolution in duplex steel.
On the Effect of Strain Reversal on Static Recrystallisation and Strain-Induced Precipitation Process Kinetics in Microalloyed Steels
Authors: Muszka K. , Sun Lin , Wynne Bradley P. , Palmiere Eric J. , Rainforth W.M.
Published: April 2012

Recent observations show that the strain reversal affects significantly and in a complex way both the static recrystallisation (SRX) and strain-induced precipitation (PPT) kinetics in Nb-microalloyed steel. It is already known that the recrystallisation stagnation is a consequence of the competition between the driving pressure for recrystallisation and the pinning pressure caused by the strain-induced precipitation of Nb (C,N) precipitates. Both of these parameters depend in turn on the local dislocation density. Thus, it is expected that a variation of the local dislocation density due to reversal of the strain will affect at the same time the local driving and the pinning pressures, which will cause the difference in the hardening levels. In the present paper, the influence of strain path change on microstructure evolution and mechanical behaviour in Nb-microalloyed steel (API X-70 grade) was studied. The deformation schedules were designed in order to investigate an effect of strain reversal on both static recrystallisation and strain-induced precipitation process kinetics. Flow curves recorded during deformation of X-70 steel showed clear influence of applied strain path on both static recrystallisation kinetics and strain-induced precipitation process.
Role of Inclination Dependent Anisotropy on Boundary Populations during Two-Dimensional Grain Growth
Authors: Kar Debashis , Sintay Stephen D. , Rohrer Gregory S. , Rollett Anthony D.
Published: April 2012

A Monte Carlo model is presented, in which the interface anisotropy is primarily inclination dependent. A dual grid method is used to determine boundary inclination in discretized digital microstructures. Evolution of the grain boundary character distribution (GBCD) in polycrystalline systems, from an initially random distribution, is inversely correlated with the anisotropy in interfacial energy, as expected.
Controlling Grain Size in Oxide Ceramics for Optimization of Strength and Wear Resistance
Authors: Rainforth W.M. , Zeng P. , Ma L.
Published: April 2012

t is well known that alumina ceramics undergo a time dependent wear transition during sliding wear. The transition, which is associated with 1-2 orders of magnitude increase in specific wear rate, involves a change from mild wear to intergranular fracture. The transition is strongly grain size dependent, with the time to the transition decreasing with grain size. However, there is a minimum grain size that can be achieved in fully dense alumina using commercially viable processing. Alternative strategies for reducing grain size and increasing toughness are through the addition of a fine second phase, with SiC and ZrO2being the most promising. The resultant composite not only has finer grain size, but also exhibits additional toughening mechanisms. This paper reports on the microstructural control in alumina, zirconia toughened alumina and alumina-silicon carbide composites. The grain size and residual stress distribution are related to the damage accumulation mechanism that occur during frictional contact, in particular the surface specific dislocation activity.
Origin of Goss Texture during Secondary Recrystallisation in Silicon-Steel
Authors: Hutchinson W. Bevis
Published: April 2012

Primary recrystallised sheets of 3% silicon steel from two different industrial processing routes have been examined after laboratory annealing to initiate secondary recrystallisation. Metallography included etching to reveal individual dislocations and sub-boundaries as well as EBSD in scanning electron microscopy. Residual low angle boundaries are not normally observed inside the secondary grains. The growth of secondaries appears to occur in a jerky manner, associated with local intrusions into the primary matrix that destabilise the interface. The frequency of occurrence of special low energy grain boundaries such as 9 and 5 is believed to dictate the selectivity of the Goss orientation in both types of steel sheet.
Zener Pinning Pressure in Tempered Martensite Lath Structure
Authors: Kolesnikov Dmitro , Belyakov Andrey , Kipelova Alla , Dudko Valeriy , Kaibyshev Rustam , Molodov Dmitri A.
Published: April 2012

The Zener drag force exerted by M23C6carbides, Fe2(W,Mo) Laves phase and M(C,N) particles for migration of different grain boundaries in P92-type and P911+3%Co heat-resistant steels was calculated. In particular, the prior austenite grain boundaries (PAGB), boundaries of packets and blocks, which are mainly high-angle boundaries (HAGB), were addressed. Zener pinning pressures were determined for each type of dispersoids separately taking into account that the M23C6carbides, Fe2(W,Mo) Laves phase are inhomogeneously distributed such that they are mainly located at the boundaries, and the M(C,N) dispersoids are uniformly distributed throughout the metallic matrix. In the both steels, the pinning pressure from the second phase particles located at grain boundaries is about an order of magnitude higher than that caused by homogeneously distributed MX precipitates. In spite of numerous second phase particles precipitated during tempering, grain growth (although rather moderate) occurred during the creep tests of the studied materials. The driving pressure for grain boundary motion might be mostly associated with high dislocation density retained in the tempered martensite structure. The resulting pressure for grain growth in the P92-type steel under creep conditions at 600 and 650°C is somewhat higher than that for the P911 steel.
Microstructure Evolution in Sintering of Alumina-Zirconia Ceramics Simulated by a Modified Phase Field Method
Authors: Wei Cheng Yang , Li Sai Yi
Published: April 2012

The densification and grain growth during sintering of alumina-zirconia (Al2O3ZrO2) ceramics were simulated using a modified phase field method, which considered simultaneously a density field, a composition filed and orientation fields. The results indicate that the model can capture the main microstructure features in the different stages of sintering. A higher relative green density leads to a higher final density and a larger final grain size in the sintered ceramics. A higher volume fraction of the ZrO2 phase results in a lower relative density and a smaller final grain size.
Grain Size Distributions and Evolution Equations in Nanocrystalline Grain Growth
Authors: Streitenberger Peter , Zöllner Dana
Published: April 2012

Size effects observed in nanocrystalline grain growth are modeled by attributing each type of grain boundary junction an own specific energy and finite mobility. By considering grain growth as a dissipative process that is driven by the reduction of the Gibbs free interface and junction energy a general grain evolution equation is derived that separates into nine types of possible growth kinetics. The corresponding self-similar grain size distributions are derived and compared with results from modified Monte Carlo Potts model simulations taking into account size effects in triple and quadruple junction limited grain growth.
EBSD Analysis of Deformed and Partially Recrystallized Microstructures in ECAE-Processed Copper
Authors: Mishin O.V. , Bowen J.R. , Godfrey Andrew
Published: April 2012

The deformed microstructure and recrystallization behavior of copper samples processed using equal channel angular extrusion (ECAE) have been investigated. The heavily deformed microstructure was found to be non-uniform through the sample thickness and to vary in a manner consistent with the non-uniform distribution of strain imposed by processing. The through-thickness heterogeneity of the deformed microstructure resulted in a different extent of recrystallization in different layers during annealing. Recrystallized grains were also observed in samples that were not annealed, but stored at room temperature, which indicates that the deformed microstructure of ECAE-processed pure copper is unstable even at room temperature. In each sample, recrystallization was found to initiate in regions containing predominantly large misorientations.
Effect of Partially Recrystallized Structure Produced by Intense Plastic Deformation on Fatigue Behavior of an Al6%Mg0.3%Sc Alloy
Authors: Avtokratova Elena , Sitdikov Oleg , Kaibyshev Rustam
Published: April 2012

t was shown that ECAP of an Al6%Mg0.3%Sc through route C at a temperature of 325°C (0.6Tm) to a total strain of 8 leads to the formation of partially recrystallized structure; the average size and the volume fraction of new ultrafine grains (UFG) were 1.2μm and 0.7, respectively. Areas of UFG structure alternate with coarse remnant parts of deformed original grains. Effect of this bimodal structure on room-temperature mechanical properties including fatigue behavior is examined. The ECAP processing led to increase in the yield strength and endurance limit accompanied with an insignificant loss of plasticity. Analysis of the surface features indicated that the fracture upon cyclic loading occurred by the transgranular mode in the regions of the unrecrystallized grains; this followed from the presence of striations in the large flat regions of the samples. In contrast, the fracture within regions of UFG grains occurred by the intergranular mode; distinct boundaries were clearly observed between the adjacent facets. It is concluded that the ultrafine grains presenting in the bimodal structure increase the strength characteristics of the alloy whereas the large remnant grains provide its relatively high plasticity. Therefore, the bimodal structure produced by the ECAP may ensure a certain balance between the rate of nucleation and propagation of a fatigue crack. The influence of this microstructure on the fatigue behavior of the material is discussed in detail.
The Effect of High Temperature Grain Refinement on the Isothermal Ferrite Grain Growth Kinetics in Steel S460
Authors: Hinton J.S. , Palmiere Eric J. , Rainforth W.M.
Published: April 2012

Plate steel S460 is intercritically rolled during the final stages of industrial processing. A series of experiments to represent the preliminary stages of an intercritical simulation were completed and the isothermal austenite to ferrite transformation kinetics investigated. The growth of the ferrite grains was interpreted using the classic JMAK model and the effect of processing history also examined. A double austenite deformation at 1323 K, to a true strain of 0.2, led to the most acceptable starting microstructure for the extended simulation. The role of niobium in this preliminary simulation is also considered.
Microstructure Evolution during Annealing Treatment of Austenitic Stainless Steels
Authors: Herrera Clara , Padilha Angelo Fernando , Plaut R.L.
Published: April 2012

Austenitic stainless steels of the AISI 304 and 316 grades, amongst over other hundred compositions of stainless steels available in the market, are the most frequently used ones worldwide. They are selected for numerous applications due to their favorable combination of characteristics such as low price, moderate to good corrosion resistance, excellent ductility and toughness along with good weldability. Their major limitation is in the yield strength, which is relatively low (about 200 MPa), in the annealed condition. Through cold working, this value can be easily multiplied by a factor of up to six, however ductility drops. The cold worked sub-structure of the austenitic stainless steels is formed by a planar array of dislocations and strain induced martensites, α (BCC) and ε (HCP). The microstructure evolution of austenitic stainless steels, AISI 304L and 316L, during cold rolling and subsequent annealing was studied (maximum thickness reduction - 90%). Samples were initially solution annealed at 1100°C for one hour with subsequent water quenched. Following, they have been cold rolled at room temperature, with cold reductions varying between 10 and 90%. After rolling, samples with approximately 90% thickness reduction have been submitted to annealing treatments in order to study martensite reversion, recovery and recrystallization. Annealing treatments have been performed between 200 and 900°C, with 100°C interval for one hour. The resulting microstructures were investigated by optical microscopy, scanning electron microscopy (with EBSD), magnetic measurements and hardness evaluation. As received (hot rolled) austenitic stainless steel sheet presented recrystallized equiaxial grains with austenite and islands of delta ferrite, in larger quantities mainly in the centre of the sheet. The solution annealing at 1100°C for one hour eliminated delta ferrite. During rolling, the austenite partially transforms into α martensite. The 50% αmartensite reversion temperature is close to 550°C for both steels. This temperature is practically independent of the amount of αmartensite present in the steel. The 50% recrystallization temperature of the 304L steel is lower than that of the 316L steel, about 700 and 800°C, respectively. The 316L steel shows a higher recrystallization resistance, due to its higher SFE and lower storage deformation energy than the 304L steel. Recrystallization temperature is about 150°C higher that the αmartensite reversion temperature. The percentage of αmartensite has a strong influence on the recrystallized grain size, the higher the percentage of this phase the smaller will be the grain size.