bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT OF HIGH STRENGTH Mg-Cu-Zn ULTRAFINE EUTECTIC COMPOSITES WITH ENHANCED PLASTICITY
Authors: SONG KIAN , KIM KI BUEM , PARK JIN MAN , LEE JAE SEOL , PARK JOON SIK , LEE WON HEE , KIM DO HYANG
Published: April 2009

Mg - Cu - Zn ultrafine eutectic composites with different length scale heterogeneity, consisting of micrometer size dendrites and/or ultrafine scale bimodal eutectics, exhibit high yield strength as well as good plasticity at room temperature compression. Among these alloys, micron-scale α- Mg dendrites reinforced ultrafine eutectic composites exhibit high yield strength of 310 ~ 420 MPa and large plasticity of 7 ~ 12%. Meanwhile, a Mg 72Cu5Zn23 alloy comprising a bimodal eutectic structure without the micron-scale α- Mg dendrites shows the optimized mechanical properties the highest yield strength of 455 MPa combined with a considerable plastic strain of ~5%.
INFLUENCE OF ELECTROLYTIC PLASMA OXIDATION COATING ON TENSILE BEHAVIOR OF DIE-CAST AM50 ALLOY SUBJECTED TO SALT CORROSION
Authors: HAN LIHONG , NIE XUEYUAN , ZHANG PENG , ZHANG QIANG , HU HENRY
Published: April 2009

Three different thickness ceramic coatings were deposited on die-cast AM50 magnesium alloy in KOH and NaAlO 2 solution using electrolytic plasma oxidation (EPO) technology for corrosion prevention. Immersion corrosion tests were carried out in 3.5% NaCl solution for 336 hours to investigate the effect of coating thicknesses on tensile and fracture behaviors of the coated AM50 alloys. The results show that the yield strength (YS) and ultimate tensile strength (UTS) of the coated AM50 alloy subjected to immersion corrosion increase with an increase in coating thicknesses. Further analyses on stress and strain curves indicate that the coating enhances the strain-hardening rates of the corroded alloy during its plastic deformation. SEM examination on the fractured surface manifests that the substrate AM50 alloys exhibit characteristics of ductile deformation with deep dimples. However, brittle features prevail on the fractured surface of the mixed layer of coating plus oxidation corrosion product. Micro cracks were observed between the mixed layer and the AM50 alloy substrate induced by corrosion and within the mixed layer induced by EPO process, which could be responsible for the brittle fracture.
EFFECT OF SCANDIUM ON THE CORROSION BEHAVIOR OF THE CASTING Al-Cu ALLOYS IN NACL SOLUTION
Authors: ZHAO WENGUI , WANG JINGUO , HOU JINGQI , JIANG QICHUAN
Published: April 2009

Corrosion behavior of the casting Al - Cu alloys with and without Sc addition was studied by both the immersion test and electrochemical measurement methods. The results show that pitting corrosion was found on the surfaces of these alloys in 3.5 wt .% NaCl solution, while the corrosion resistance of the Al - Cu alloys with Sc is better than that of the Al - Cu alloy without Sc . With increasing Sc content, the corrosion resistance of the present Al - Cu alloys varies significantly, and the 0.1 wt .% Sc alloy has the best corrosion resistance. Also, the corrosion potential of the present alloys with Sc is shifted positively compared with that of the alloy without Sc by electrochemical measurement, indicating that the alloys with Sc have better corrosion resistance. The microstructures of the Al - Cu alloys change from the coarse grains to the fine equiaxed grains due to Sc addition, which is responsible for the reduced susceptibility to corrosion and the enhanced corrosion resistance of the present alloys.
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AZ31 MAGNESIUM ALLOY SHEET BY HOT ROLLING
Authors: MIAO QING , HU LIANXI , WANG ERDE , LIANG SHUJIN , CHAO HONGYING
Published: April 2009

AZ31 magnesium alloy sheets with a thickness of about 2mm were prepared by using a unique hot rolling process which was featured by heating the rolls during rolling. Two different rolling routes were used to achieve the final thickness through 6 passes of rolling. The major rolling parameters were chosen as the same for both rolling routes except that the roll temperature was set to be 400°C for route A and the 1st to 4th passes of route B, but lowered to 350°C for the 5th and 6th passes of route B. The microstructure and mechanical properties of the alloy sheets were comparatively investigated. The results showed that dynamic recrystallization occurred during hot rolling, and by choosing the processing parameters appropriately the grain size could be refined steadily with increasing rolling passes. The final alloy sheet prepared by 6 passes of rolling via the rolling route B was featured by a very fine microstructure, with the grain size being 5μm in average. Correspondingly, it presented very high strength and tensile elongation, with its yield strength and tensile elongation achieving 206MPa and 26.4% in the transverse, and 196MPa and 27.6% in the rolling direction, respectively.
PROCESSING-PROPERTY RELATIONSHIPS OF AS-CAST MAGNESIUM FOAMS WITH CONTROLLABLE ARCHITECTURE
Authors: KIRKLAND NICHOLAS T. , KOLBEINSSON INGOLFUR , WOODFIELD TIM , DIAS GEORGE , STAIGER MARK P.
Published: April 2009

An inverse template method that relies on the use of a controlled porous spacer material was implemented to produce periodic magnesium (Mg) foams. Bulk infiltration pressures were varied to determine a processing-property map. The microstructure and mechanical properties of the resulting periodic Mg foams were investigated using optical and scanning electron microscopy (SEM), and compression testing, respectively. SEM was also used to analyze the surface topology of the periodic foams and compare it to the original template material. It was found that the casting pressure has a great effect not only on the success of the infiltration but also the surface roughness and other microstructural features of the foam.
BLUE LIGHT EMISSION FROM STRESS-ACTIVATED SR2MGSI2O7:EU
Authors: ZHANG HONGWU , TERASAKI NAO , YAMADA HIROSHI , XU CHAO-NAN
Published: April 2009

We discovered that Sr 2 MgSi 2 O 7: Eu phosphor emits blue light under the application of a mechanical stress, a phenomenon known as mechanoluminescence (ML). The ML showed a similar spectrum as photoluminescence (PL), which indicated that ML is emitted from the same center of Eu 2+ ions as PL. The analysis of structure and thermoluminescne suggested that the origin of ML for Sr 2 MgSi 2 O 7: Eu phosphor can be attributed to strain-induced electroluminescence, that is, piezoelectricity impelled the trapped electrons to escape from the trap and produce ML . Furthermore, the relation between ML intensity and compressive load is close to linearity, which indicate that this sample can be used for smart-skin and self-diagnosis applications.
STRAIN RATE DEPENDENCE ON THE HIGH TEMPERATURE MECHANICAL BEHAVIOR OF THE NI-18SI-3.0NB-1.0CR-0.2B INTERMETALLIC ALLOY
Authors: FU CHIH-CHIANG , JANG JASON SHIAN-CHING , LEE I-SUI , WANG HUEI-SEN
Published: April 2009

The effect of strain rate and temperature on the mechanical behavior of the Ni -18 Si -3.0 Nb -1.0 Cr -0.2 B alloy was investigated by atmosphere-controlled tensile testing in vacuum and air atmosphere at different strain rates and different temperatures. The results reveal that the Ni -18 Si -3.0 Nb -1.0 Cr -0.2 B alloy exhibits ductile mechanical behavior (UTS > 1200 MPa, ε > 8%) at room temperature under different atmosphere conditions. In addition, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 973K. The elongation of the samples tested in vacuum and air for the Ni -18 Si -3 Nb -1 Cr -0.2 B alloy exhibits a significantly increase with temperature from 973K to 1073K. In addition, all fracture surfaces tested at 1073K in vacuum and air atmosphere presents a typical ductile fracture surface, a fully dimpled fracture pattern. The fact of increasing in elongation at high temperature (1073K) is suggested to be attributed by the dynamic recrystallization that occurs preferentially around the dispersion phase or grain boundaries and so as to enhance the ductility by reducing the stress concentration at or near grain boundaries.
EVOLUTION OF MICROSTRUCTURE AND MECHANICAL PROPERTIES OF THE Ni-25Al-27.5Fe-1.0Nb INTERMETALLIC ALLOY AFTER THERMAL MECHANICAL TREATMENT
Authors: FU CHIH-CHIANG , JANG JASON SHIAN-CHING , TSAI HAN-CHANG , LI TSUNG-HSIUNG
Published: April 2009

The evolution of microstructure and mechanical properties of the Ni -25 Al -27.5 Fe -1.0 Nb intermetallic alloy after thermal mechanical treatment (TMT) was systematically investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) with electron dispersive spectrum (EDS) capability, and atmosphere-controlled tensile test at room temperature with different strain rate. The results of XRD reveals that a matrix of β' phase [( Ni , Fe ) Al type ordered bcc structure] and a precipitated γ phase ( Ni 3 Fe fcc solid solution) co-exist in this alloy after TMT. The dendritic microstructure of the as-cast alloy was eliminated after TMT process. In parallel, a refined and homogeneous distributed lath precipitates can be obtained after annealing at 820 for 4 hr. Additionally, this alloy presents a relative high strength as well as ductile mechanical behavior (UTS~1320 MPa and ε~8%, respectively) at room temperature in air. A 30% improvement in yield strength is suggested to be contributed by the refined microstructure from the TMT. Moreover, the tensile strength and ductility of this alloy exhibit insensitive response with respect to the loading strain rate at room temperature.
THE COMPOSITION AND TEMPERATURE EFFECTS ON THE ULTRA HIGH STRENGTH STAINLESS STEEL DESIGN
Authors: XU W. , DEL CASTILLO P. E. J. RIVERA DÍAZ , VAN DER ZWAAG S.
Published: April 2009

Alloy composition and heat treatment are of paramount importance to determining alloy properties. Their control is of great importance for new alloy design and industrial fabrication control. A base alloy utilizing MX carbide is designed through a theory guided computational approach coupling a genetic algorithm with optimization criteria based on thermodynamic, kinetic and mechanical principles. The combined effects of 11 alloying elements ( Al , C , Co , Cr , Cu , Mo , Nb , Ni , Si , Ti and V ) are investigated in terms of the composition optimization criteria: the martensite start (Ms) temperature, the suppression of undesirable phases, the Cr concentration in the matrix and the potency of the precipitation strengthening contribution. The results show the concentration sensitivities of each component and also point out new potential composition domains for further strength increase. The aging temperature effect is studied and the aging temperature industrially followed is recovered.
PREDICTION OF MECHANICAL PROPERTIES OF 25CrMo48V SEAMLESS TUBE USING NEURAL NETWORK MODEL
Authors: SUN LAIBO , ZHANG CHUANYOU , WANG QINGFENG , WANG MINGZHI , YAN ZESHENG
Published: April 2009

In this investigation, a neural network model was established to predict mechanical properties of 25 CrMo 48 V seamless tubes. The sensitivity analysis was also performed to estimate the relative significance of each chemical composition in mechanical behavior of steel tubes. The results of this investigation show that there is a good agreement between experimental and predicted values indicating desirable validity of the model. Among those alloying elements, the elements of carbon, silicon and chromium tended to play a more important role in controlling both the yielding strength and the Charpy-V-Notch transverse impact toughness. In comparison, the impurities such as O , N , S and P have a relatively weak impact. More detailed dependences of mechanical properties on each chemical composition in isolation can be revealed using the established model. The well-trained neural network has a great potential in designing tough and ultrahigh-strength seamless tubes and modeling the on-line production parameters.
EVOLUTION OF RECRYSTALLIZATION MICROSTRUCTURE AND TEXTURE IN LOW CARBON CSP STEEL DURING ANNEALING
Authors: WANG HAIYAN , TIAN RONGBIN , REN HUIPING , JIN ZILI
Published: April 2009

Microstructure evolution and texture formation in low carbon CSP steel were observed by means of metallgraphic, TEM, and SEM equipped with electron back scattered diffraction (EBSD) system. The influence of large particles and fine carbonitrides precipitates on recrystallization and texture formation during the annealing procedure was analyzed with Small Angle X-ray Scattering (SAXS) technique in the steel. It was found that the fine precipitates present in the steel have shown ability to stimulate recrystallization nucleation and transformation during deformation, but hard to accelerate recrystallization growth because of grain boundary pinning effects in the steel. Compared with the conventional low carbon steel, the recrystallization texture and microstructure of the CSP steel show distinct character, and thus modify the mechanical behaviour of the final products.
CHARACTERIZATION AND PHOTOCATALYTIC ACTIVITY OF Zn2SnO4 NANOSTRUCTURES SYNTHESIZED VIA HYDROTHERMAL METHOD
Authors: WU YU-SHIANG , LEE YUAN-HAUN , FENG CHUN-LIANG
Published: April 2009

Nanosized zinc stannate Zn 2 SnO 4 ( ZTO ) was synthesized via a simple hydrothermal method using sodium hydroxide NaOH as a mineralizer. Hydrothermally treated at 150, 200, and 250°C for 24 h and 48 h, the X-ray diffraction (XRD) pattern showed that highly crystalline ZTO nanostructures could be formed at 200 and 250°C. Transmission electron microscopy (TEM) images showed that ZTO nanocubes were formed at 250°C, and a sheet-like structure was found at 200°C. Raman spectra revealed that ZTO had a spinel structure and there were two Raman shift peaks at approximately 668 and 535 cm-1, which were similar to the peaks of ZTO nanowires. Furthermore, the photocatalytic activity of the ZTO samples was assessed utilizing methylene blue (MB) under ultraviolet irradiation, and the UV-Visible light absorption spectra was investigated to interpret the relationship between photocatalytic properties and light absorptivity. The sheet-like ZTO nanostructures exhibited better photocatalytic activity due to their excellent light absorption properties.
PREDICTING Ms TEMPERATURE APPLYING PRINCIPAL COMPONENT ANALYSIS-ARTIFICIAL NEURAL NETWORKS
Authors: XU XUEXIA , BAI BINGZHE , YOU WEI
Published: April 2009

The principal component analysis-artificial neural network (PCA-ANN) model was developed to predict martensite transformation start temperature ( Ms ) of steels. Training samples were processed by principal component analysis and the number of input variables was reduced from 6 to 4, then the scores of principal components were used to establish new sample database to train the ANN model. Ms of steels were predicted by the PCA-ANN model. The predicted and measured Ms distribute along the 0-45° diagonal in the scatter diagram and the statistical errors are MSE-16.0256, MSRE-4.49% and VOF-1.97790 respectively. Comparing the prediction results of different models it is shown that the accuracy of the PCA-ANN model was the highest, which indicated that the principal component analysis was helpful to improve the prediction accuracy of ANN model.
REFINED DENDRITE AND PRECISE ORIENTATION OF NICKEL-BASED MONOCRYSTAL SUPERALLOY WITH MELT SUPERHEATING TREATMENT
Authors: ZOU MINMING , ZHANG JUN , LI BO , LIU LIN , FU HENGZHI
Published: April 2009

Ni -based monocrystal superalloy with fine dendrite, precise orientation and finally elevated service performance is required as turbine blades in advanced aeroengine. In this paper, the melt superheating treatment is carried out for DD3 single crystal superalloy during directional solidification processing. The thermal gradient of solidification interface remains constant for different melt superheating temperatures with the appropriate superheating treatment regulation. It is shown that with the melt superheating temperature increased from 1500°C to 1640°C and then to 1780°C respectively, both the primary and the secondary dendrite arms are obviously refined and the dendrite segregation ratios of Mo , W and Ti are reduced while the deviation angle of (001) crystal orientation can all be controlled within 5°. The dendrite structure refinement and the crystal orientation consistence should be attributed to the melt structure change and heredity which is caused by the superheating treatment.
INFLUENCE OF NITROGEN ON HOT DUCTILITY BEHAVIOR OF MEDIUM CARBON MICROALLOYED STEEL
Authors: ZHAO SUJUAN , WANG QINGFENG , YAN ZESHENG
Published: April 2009

The current study aims to estimate the influence of enhanced nitrogen on the hot ductility of medium carbon microalloyed steel. For this purpose, hot tensile tests were carried out at temperatures rangeing from 700°C-1000°C at a true strain rate of 0.001s-1. The fracture surfaces and their neighboring precipitates and matrix microstructures "frozen" in tensile temperatures were observed. The dependence of hot ductility on the fracture mode and in situ microstructural changes were discussed. The results indicate that raising the nitrogen content from 0.003% to 0.014% and 0.021% was found to deteriorate the ductility as the obtained ductility trough became deeper and wider. The trough deepening caused by the addition of nitrogen was due to the formation of film-like ferrite and fine VN precipitation along the austenite grain boundaries promoting low ductility intergranular failure. On the other hand, the retarded dynamic recrystallization, the promoted deformation induced ferrite formation and precipitation at higher temperatures by enhanced nitrogen were regarded as the possible reasons for a wider trough. In summary, the above results indicate the hot ductility of medium carbon microalloyed steels is weakened to some extent by enhanced nitrogen and their windows suitable for continuous casting should be schemed very carefully.
EFFECT OF COBALT AND NICKEL ON THE STRUCTURAL STABILITY FOR FE3C: FIRST-PRINCIPLES CALCULATIONS
Authors: WANG XIANGRONG , YAN MUFU
Published: April 2009

In this paper, the effect of Co and Ni in AerMet100 steel on the structure stability for Fe 3 C was investigated using first-principles calculations based on generalized gradient approximation (GGA) density function theory. The internal positions of atoms within the unit cell were optimized and the ground state properties such as lattice parameter, the formation energy and density of states for Fe 3 C structure without and with Co or Ni (( Fe , M )3 C , M = Fe , Co , Ni ) were calculated. The calculated results show that the equilibrium structural parameters of Fe 3 C agree with the experimental ones. The formation energy of Fe 3 C is negative, while that of Fe 3 C with Co or Ni are positive. The Fe 3 C with the substitution of Co or Ni for Fe at the 4c sites are metastable or unstable at ambient conditions. The effect of Co and Ni on the structural stability for Fe 3 C is discussed in terms of their electronic structure and chemical bonding.
EFFECTS OF ADDITIONAL ELEMENTS ON THE EVOLUTION OF SECOND PHASES IN 9-12%CrSTEEL AND RESULTING MECHANICAL PROPERTIES
Authors: DONG JILING , YU HUI , YOO DAE-HWANG , HUYNH QUOCBAO , SHIN KEESAM , KIM MINSOO , KANG SUNGTAE
Published: April 2009

Investigated in this study are precipitate evolution with and without addition of W , Co , and B in two kinds of 9-12% Cr steels (named as A and B ) used for power plants after various aging time and temperature using OM, SEM, TEM, etc. Three kinds of precipitates ( Cr -rich M23C6, Nb -rich and V -rich MX, W -rich and Mo -rich Laves phase) were observed and investigated in the two alloys. Upon aging, the area fraction of M23C6increased whereas that of Laves phases decreased despite of increase in size. The area fraction of W -rich Laves phase was much higher than that of Mo -rich Laves phase, indicating that W addition, compared to that of Mo addition, is more powerful in the formation of Laves phase precipitation (specimen A ). The martensitic microstructure of specimen B was more stable than that of specimen A due to the addition of cobalt and boron. The tensile test and impact test were measured and studied in relation to the long term aging effect.
Al2O3/ZrO2 (Y2O3) PREPARED BY COMBUSTION SYNTHESIS UNDER HIGH GRAVITY
Authors: ZHANG LONG , ZHAO ZHONGMIN , SONG YIGANG , WANG WEIGUO , LIU HONGBO
Published: April 2009

By introducing ZrO 2 (4 Y ) powder into the thermit, Al 2 O 3/ ZrO 2 (4 Y ) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al 2 O 3/33% ZrO 2 (4 Y ) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t - ZrO 2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t - ZrO 2 grains; meanwhile, Al 2 O 3/45% ZrO 2 (4 Y ) were comprised of spherically-shaped micron-meter t - ZrO 2 grains. Similar to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the increase in hardness and flexural strength of Al 2 O 3/33% ZrO 2 (4 Y ) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al 2 O 3/45% ZrO 2 (4 Y ) was considered to be a result of the fine spherically-shaped t - ZrO 2 grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.
THERMAL SHOCK BEHAVIOR OF ZrB2-20vol.%SiC-15vol.% GRAPHITE FLAKE BY HOT PRESSING
Authors: ZHANG XINGHONG , WANG ZHI , SUN XIN , HAN WENBO , HONG CHANGQING
Published: April 2009

The thermal shock behavior of hot-pressed ZrB 2- SiC composite containing 15vol.% graphite flake ( ZrB 2- SiC - G ) was investigated. The thermal shock testing was carried out by means of quenching into water from high temperatures (Δ T in the range of 200-1000°C). The damage introduced by the thermal shock was characterized by the degradation of bending strength. The residual strength exhibited a complex evolution and could be divided into three zones according to the variation of the temperature difference: (i) no damage zone (200-300°C), (ii) strength degradation zone (300-400°C), and (iii) low stable strength zone (400-1000°C). The minimum residual strength of 160 MPa, higher than 40% of the initial strength of 396 MPa, was obtained in the third zone of temperature difference. The surface feature of ZrB 2- SiC - G composite after the thermal shock tests was also investigated.
HIGH TEMPERATURE OXIDATION OF CaB6-28wt%Ni SINTERED BODY
Authors: ZHANG LIN , MIN GUANGHUI , YANG LIXIA , YU HUASHUN
Published: April 2009

The oxidation process of calcium hexaboride ( CaB 6) ceramic sintered body with 28wt% nickel as a sintering aid was investigated systematically in this paper. DTA-TG was used to analyze the oxidation behavior at various temperatures. The morphologies of the oxidation surfaces and the interface between the oxide layer and the bulk material were given by EPMA and BSE, respectively. Element distribution on cross-sections was measured by an energy spectrum analyzer. It is found that CaB 6-28 wt % Ni shows an excellent oxidation resistance below 1173K owing to the protection provided by calcium borate on the surface. Catastrophic fast oxidation begins at 1273K. The grain boundaries act as the diffusion channels for O 2 penetration. The existence of Ni doesn't affect the oxidation behavior of the matrix CaB 6. The mechanism of oxidation was also discussed in this paper.
DIELECTRIC PROPERTIES OF Ca(1-x)ZnxLa4Ti5O17 CERAMICS AT MICROWAVE FREQUENCIES
Authors: Chen Yih-Chien , Tsai Jian-Min
Published: April 2009

In this paper, the microwave dielectric properties of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics have been studied. The diffraction peaks of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics shift to higher angles as x increases from 0 to 0.01 and nearly unchanged with x increasing from 0.01 to 0.03. A maximum density of dielectric constant value of 57 and a quality factor ( Q × f ) of 15000 GHz can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h. A near-zero temperature coefficient of resonant frequency (τ f ) of -8.1 ppm/°C can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h.
EFFECT OF DEFORMATION-INDUCED TRANSFORMATION PROCESS ON FERRITE GRAIN SIZE AND VOLUME FRACTION IN STEEL 12CR1MOV
Authors: LI QINGFEN , CUI XIUFANG , CHEN HONGBIN
Published: April 2009

Effect of deformation induced transformation (DIT) process on ferrite grain size and ferrite transformation volume fraction in the refractory low alloy steel 12 Cr 1 MoV by controlled rolling and controlled cooling technology were experimentally studied. Simulation experiments of hot deformation were carried out with the Gleeble-1500 system. Single-pass and multi-pass hot rolling process with different deformation temperature, deformation reduction, strain rate and cooling rate were performed separately. The ferrite grain size decreased and the ferrite volume fraction increased with decreasing deformation temperature, and the extra-fine ferrite grain about 1.01µm was obtained when the deformation temperature reached 780°C. Higher deformation reduction resulted finer ferrite grain size and higher ferrite volume fraction. Both the ferrite grain size and ferrite volume fraction decreased with increasing strain rate. The ferrite grain size decreased but the ferrite volume fraction didn't change much when the cooling rate increased. The grain size and the ferrite volume fraction were improved more by three-passes than two-passes rolling. The mechanism of grain refinement by DIT was discussed.
ANALYSIS OF 100-METER RAIL TEMPERATURE FIELD DURING COOLING PROCESS BEFORE STRAIGHTENING BY FEM
Authors: LI GE , CUI HAIYAN , CHEN LIN
Published: April 2009

The straightness of the 100-meter rail after straightening is directly affected by the bending deformation during cooling before straightening, and the analysis of the temperature field in the cooling process is the basis of studying the bending deformation. By analyzing the heat boundary conditions in the cooling process, the temperature field was calculated and its variable law was analyzed by using the 3-D transient non-liner finite element method. The factors such as the solid-state phase change and the physical parameters with change of the temperature were considered, and the numerical results were coincident with the experimental data. The results show that the velocities of temperature changing at different positions of the rail's cross-section are different in the cooling progress, and the phase change and the irregular cross-section of rail are important influencing factors.
THE CHANGE IN THE CHEMICAL COMPOSITION AND TOUGHNESS OF API 5L-X70 WELDS BY ADDITION OF TITANIUM
Authors: BEIDOKHTI BEHROOZ , KOUKABI AMIR HOSEIN , DOLATI ABOLGHASEM , HE PENG
Published: April 2009

The objective of this work was to study the influence of titanium variations on the API 5L-X70 steel weld metal properties. The relationship between microstructure and toughness of the weld deposit was studied by means of full metallographic, longitudinal tensile and Charpy- V notch tests on the specimens cut transversely to the weld beads. The best combination of microstructure and impact properties was obtained in the range of 0.02-0.05% titanium. By further increasing of titanium content, the microstructure was changed from a mixture of acicular ferrite, grain-boundary ferrite, Widmanstätten ferrite to a mixture of acicular ferrite, grain-boundary ferrite, bainite and ferrite with M/A microconstituent. Therefore, the mode of fracture also changed from dimpled ductile to quasi-cleavage. Titanium-base inclusions improve impact toughness by increasing the formation of acicular ferrite in the microstructure. The amount of manganese in inclusions was decreased with addition of titanium to the weld metal.
EFFECT OF COEXISTENCE OF SIMILAR ELEMENTS La AND Ce ON FORMATION OF (La-Ce)-Al-Cu BULK METALLIC GLASSES
Authors: YANG QING , PANG SHUJIE , LI RAN , ZHANG TAO
Published: April 2009

Bulk metallic glasses (BMGs) in pseudo-ternary ( La - Ce )- Al - Cu system with high glass-forming ability (GFA) were synthesized based on the beneficial effect of the coexistence of similar elements La and Ce with similar atomic size and various valence electronic structures on GFA. With the coexistence of La and Ce in ( La x Ce 1- x )65 Al 10 Cu 25 system, bulk metallic glasses with diameters up to 12 mm can be produced by copper mold casting. Besides the high GFA, the ( La x Ce 1- x )65 Al 10 Cu 25 BMGs with x = 0.6 and 0.7 exhibit low glass transition temperature T g around 362 K and wide supercooled liquid regions ΔT x (ΔT x = T x - T g , where T x is the onset temperature of crystallization) of about 80 K. Compared with ternary La - Al - Cu and Ce - Al - Cu systems, significant improvement of GFA for the ( La - Ce )- Al - Cu system is caused by the coexistence of similar elements La and Ce , and the mechanism is discussed from a thermodynamic viewpoint.
A GLASS TRANSITION MODEL FOR SHAPE MEMORY POLYMER AND ITS COMPOSITE
Authors: ZHOU BO , LIU YAN-JU , LAN XIN , LENG JIN-SONG , YOON SUNG-HO
Published: April 2009

As novel smart materials, shape memory polymer (SMP) and its composite (SMPC) have the ability to regain its original shape after undergoing significant deformation upon heating or other external stimuli such as light, chemic condition and so on. Their special behaviors much depends on the glass transitions due to the increasing of material temperature. Dynamic Mechanical Analysis (DMA) tests are performed on the styrene-based SMP and its carbon fiber fabric reinforced SMPC to investigate their glass transition behaviors. Three glass transition critical temperatures of SMP or SMPC are defined and a method to determine their values from DMA tests is supposed. A glass transition model is developed to describe the glass transition behaviors of SMP or SMPC based on the results of DMA tests. Numerical calculations illustrate the method determining the glass transition critical temperature is reasonable and the model can well predict the glass transition behaviors of SMP or SMPC.
TENSILE AND COMPRESSIVE MECHANICAL BEHAVIOR OF A CoCrCuFeNiAl0.5 HIGH ENTROPY ALLOY
Authors: WANG FANGJUN , ZHANG YONG , CHEN GUOLIANG , DAVIES HYWEL A.
Published: April 2009

A high entropy alloy of composition CoCrCuFeNiAl 0.5 is mainly composed of a face centered cubic (FCC) solid solution phase. The tensile and compressive properties of the alloy were investigated; the alloy exhibited a tensile strength of 707 MPa, together with a large plastic strain limit of 19%.
EFFECT OF ANNEALING ON THE GIANT MAGNETO-IMPEDANCE OFCO-BASED WIRES
Authors: ZHANG SHULING , XING DAWEI , SUN JIANFEI
Published: April 2009

The giant magnetoimpedance (GMI) effect in Co 75 Fe 4.2 Si 8 B 12 Nb 0.8 melt extraction wires annealed in a vacuum furnace at 450°C holding for 10min, 20min, 25min, 30min and 40min, respectively, is investigated. Strong GMI effect is observed at a typical frequency of 37MHz. The observation on the GMI effect indicates that the anisotropy field dominated by the anneal treatment is vital to the GMI ratio △Z/Z(%) and its field sensitivity. The improvement on GMI effect when anneal time is less than 20min is ascribed to the stress release, decreased anisotropy field and increased permeability. The decrease of GMI effect when anneal time is over 25min results from nanocrystalline phase grow up inducing the crystalline anisotropy field increase. Suitable annealed wires possess large GMI ratio (855%) and little anisotropy field achieving high field sensitivity to 151%/ Oe . These results indicate these Co -based melt extraction wires are excellent for using in novel field sensors applications.
EFFECT OF CRYSTALLIZATION AND SURFACE TREATMENT ON DEFORMATION AND FRACTURE OF Zr-Ti-Cu-Ni-Be BULK METALLIC GLASS
Authors: CHOI YOUNG CHUL , HONG SUN IG
Published: April 2009

In this study, the cracking behavior in the bulk and the stress-strain responses of partially crystallized Zr - Ti - Cu - Ni - Be bulk metallic glass after surface modification were investigated. The compressive plasticity was found to be dependent on the surface conditions. The plasticity was enhanced significantly by a complete removal of visible surface flaws. The electro-plating of copper on the rough surface also increased the plasticity of Zr base BMG of the present study. The beneficial effect of the electro-plating can be attributed to filling and smoothening effect due to plating and/or the ductilization of the surface, both of which does not favor crack nucleation. We also found the cracking behavior in the bulk different from the surface region. The cracks in the center of the sample were not straight, but wavy, suggesting the cracks were deflected by or attracted to crystalline particles. A high magnification view of a crack revealed small triangular shaped crystals along the crack path.
EFFECT OF HIGH MAGNETIC FIELD ON THE CRYSTALLIZATION OF MELT-SPUN FE-PT-B AMORPHOUS ALLOY
Authors: ZHANG TAO , ZHANG XINGGUO , WU NANNAN , REN ZHENG , JIA FEI , ZHANG WEI
Published: April 2009

The crystallization of melt-spun Fe - Pt - B amorphous alloy with a thickness of 20 µm in steady high magnetic field (HMF) was investigated. The intensity of the applied magnetic field is 0-10 T along with the ribbons annealed at temperature ranging from 673 K to 873 K. The direction of the performed magnetic field is perpendicular to the direction of surface velocity of the Cu wheel. The thermal magnetic properties of the samples were obtained by the thermal gravity analyzer with a magnet attached to the outside of the furnace filled with flowing inert gas. The phase transformations of Fe - Pt - B amorphous alloy on heating with and without the steady HMF were studied by X-ray diffractometry together with the melt-spun ribbon. The average grain size of the samples annealed in HMF was about 10 nm calculated from the XRD patterns. The HMF was thought to be effective on the refinement of nanograins which were produced by the crystallization of the amorphous ribbon during the annealing process.
SPRAY FORMING OF FINEMET ALLOY FE73.5CU1NB3SI13.5B9
Authors: YANG SHA , YAN BIAO , DONG PENG , GUAN LEDING
Published: April 2009

Fe -based amorphous alloys are widely used in the magnetic apparatus and generally produced by the single-roller copper-wheel melt spinning method. Spray forming is one of the rapid solidification techniques as the spinning method is, seldom used to fabricate Fe -based amorphous alloys. However in this paper, a Fe -based alloy with the nominal composition of Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ( at .%) alloy was fabricated by spray forming technique with the aim of investigating the formation of amorphous phases and novel microstructures by the high cooling rate involved in this process. The gas/metal mass flow rate used was 0.15, and nitrogen was used as the atomization gas. The resulting deposit and the overspray powder had a median diameter of about 50 μm with a total weight of about 2.2 kg. The microstructure of the deposit was observed by utilizing the X-Ray Diffraction (XRD) and Optical Microscope (OM), as well as Transmission Electron Microscope (TEM), which revealed a heterogeneous varying with the thickness, presenting at center region 15 mm and at border 8 mm with porosities 4 and 9%, respectively. The thicker region showed a fully crystalline microstructure with grain size of about 250nm, whereas the thinner region had a partially amorphous phase with an average grain size of 40nm. The overspray powder was fully crystallized with the grain size of 80nm which was calculated from XRD spectra using the Scherrer formula. The magnetic properties were measured through VSM, giving a poor magnetic saturation value of about 0.3~0.6 T . The coercive force was increased significantly.
PREPARATION AND CHARACTERIZATION OF AMORPHOUS ALLOY/POROUS SiCBi-CONTINUOUS STRUCTURE COMPOSITE
Authors: CHEN YONGLI , WANG AIMIN , ZHANG HAIFENG , HU ZHUANGQI
Published: April 2009

A new kind of composite with a bi -continuous structure was produced by pressure infiltrating melt Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 into porous SiC which was made by powder metallurgy. Microstructure investigations of the composite show that the melt alloy was fully infiltrated into the voids of porous SiC and quenched into amorphous state. Both the amorphous alloy and the porous SiC exhibit a three-dimensional interconnected net structure. The study of thermal properties reveals that the addition of porous SiC reduces the width of supercooled liquid region of the composite. The bi -continuous composite presents 2% plastic strain and ultimate strength of 1250MPa.
FABRICATION OF TWO-DIMENSIONAL PHOTONIC CRYSTALS WITH GE2SB2TE5 NANOHOLE ARRAYS BY NANOSPHERE LITHOGRAPHY
Authors: SONG KI-HO , LEE HYUN-YONG , YANG HOE-YOUNG , KIM SUNG-WON , SEO JAE-HEE , YUN SANG-DON , KIM JUN-HYUNG
Published: April 2009

Two-dimensional photonic crystals (2D-PCs) with Ge 2 Sb 2 Te 5 ( GST ) nanohole arrays were prepared by the nanosphere lithography (NSL) process. A primary factor of PCs is that the refractive index (n) and the n-modulation can be realized by using the GST films, which exhibit a reversible phase transformation between amorphous and crystalline states by laser illumination. The polystyrene (PS) spheres with a diameter of 500 nm were spin-coated on Si substrate and subsequently reduced by O 2-plasma treatment. The reduced spheres were utilized as a lift-off mask of the NSL process and their size and separation could be precisely controlled. Amorphous GST films were thermally evaporated and then the reduced PS spheres were removed. The fabricated GST nanohole arrays were observed by SEM and AFM. The nanohole diameters are nearly linearly reduced with increasing plasma-treatment time (t). The reduction rate (δ) for the conditions of this work was evaluated to be ~ 0.92 nm/s. The period (Λ) and filling factor (η) of PCs are structure parameters that determine their photonic bandgaps (PBGs). η-modulation can be easily achieved via a control of t and the Λ can be also modulated by the use of PS spheres with specific diameter. In addition, the PBGs for the fabricated GST 2 D PC were calculated by considering the amorphous and crystalline states of GST .
BONDING OF ALUMINA AND METAL USING BULK METALLIC GLASS FORMING ALLOY
Authors: ZHANG JINJUN , GU JIANSHENG , LI LEI , HUAN YONG , WEI BINGCHEN
Published: April 2009

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al 2 O 3 ceramic using Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.
IMPROVEMENT OF PLASTICITY OF TI-BASED BULK METALLIC GLASSES BY PHASE TRANSITION OF A COOLING MEDIUM
Authors: SHAN SHENGFENG , ZHAN ZAIJI , JIA YUANZHI , FAN CHANGZENG , ZHANG BAOQING , LIU RIPING , WANG WENKUI
Published: April 2009

Ti -based bulk metallic glasses (BMGs), Ti 40 Zr 25 Cu 9 Ni 8 Be 18, were prepared by phase transition cooling (PTC) and copper mould casting(CMC) technology. Ti 40 Zr 25 Cu 9 Ni 8 Be 18 glassy rod of more than 13 mm in diameter was prepared by PTC technology which shows the high cooling rate obtained by this technology. No obviously differences in thermal property were found between the BMGs prepared by the PTC and CMC technology. The compressive plasticity of the alloy was apparently changed, from 8% using CMC to 37% by using PTC technology. PTC technology is probably a promising method for preparing BMG and an effective way to increase the plasticity of BMGs.
SAMPLE-SIZE EFFECTS ON THE COMPRESSION BEHAVIOR OF ANi-BASED AMORPHOUS ALLOY
Authors: LIANG WEIZHONG , ZHAO GUOGANG , WU LINZHI , YU HONGJUN , LI MING , ZHANG LIN
Published: April 2009

Ni42Cu5Ti20Zr21.5Al8Si3.5bulk metallic glasses rods with diameters of 1 mm and 3 mm, were prepared by arc melting of composing elements in a Ti -gettered argon atmosphere. The compressive deformation and fracture behavior of the amorphous alloy samples with different size were investigated by testing machine and scanning electron microscope. The compressive stress-strain curves of 1 mm and 3 mm samples exhibited 4.5% and 0% plastic strain, while the compressive fracture strength for 1 mm and 3 mm rod is 4691 MPa and 2631 MPa, respectively. The compressive fracture surface of different size sample consisted of shear zone and non-shear one. Typical vein patterns with some melting drops can be seen on the shear region of 1 mm rod, while fish-bone shape patterns can be observed on 3 mm specimen surface. Some interesting different spacing periodic ripples existed on the non-shear zone of 1 and 3 mm rods. On the side surface of 1 mm sample, high density of shear bands was observed. The skip of shear bands can be seen on 1 mm sample surface. The mechanisms of the effect of sample size on fracture strength and plasticity of the Ni -based amorphous alloy are discussed.
MECHANICAL PROPERTY OF A NEW Zr-BASED BULK METALLIC GLASS WITH CERTAIN PLASTICITY AT LOW TEMPERATURE
Authors: SUN YAJUAN , QU DONGDONG , SHEN JUN , HUANG YONGJIANG , WEI XIANSHUN
Published: April 2009

The mechanical property of a new bulk metallic glass Zr 50.7 Cu 28 Ni 9 Al 12.3, which owns 5% room-temperature plasticity, is investigated at low temperatures 193K and 123K. It is indicated that the yield strength and the plasticity significantly increase by 12.8% and 50% respectively as testing temperature is lowered from 298K (at room temperature) to 123K (in liquid nitrogen). The dense and multiple shear bands which contribute to the improved ductility are observed on the side surface of these samples fractured at low-temperature. Detailed study of the stress-strain curves for the samples deformed at low temperature show that more serrations and smaller stress drop form due to generation of more much shear bands.
THE YIELD BEHAVIOR AND YIELD CRITERION OF BULK METALLIC GLASS
Authors: HU JIBIN , CHEN DEMIN
Published: April 2009

In order to define the relation between yield behavior and yield criterion of bulk metallic glass (BMG), analysis and investigations have been carried out for interrelations between yield strengths and the angle which fracture plane deviates from the 45° plane of the maximum shear stress in tensile and compressive test of BMG. Tensile fracture angle is consistent with the result calculated by theory of disconnected slip line field and Mises yield condition. Compressive fracture angle is consistent with the result calculated by Coulomb yield condition. Conclusion: BMG obeys different yield criterions in different stress states. For tensile, it follows Mises criterion, and for compression, it follows Coulomb criterion.
COMPUTATIONAL DESIGN FOR MULTIFUNCTIONAL MICROSTRUCTURAL COMPOSITES
Authors: CHEN YUHANG , ZHOU SHIWEI , LI QING
Published: April 2009

As an important class of natural and engineered materials, periodic microstructural composites have drawn substantial attention from the material research community for their excellent flexibility in tailoring various desirable physical behaviors. To develop periodic cellular composites for multifunctional applications, this paper presents a unified design framework for combining stiffness and a range of physical properties governed by quasi-harmonic partial differential equations. A multiphase microstructural configuration is sought within a periodic base-cell design domain using topology optimization. To deal with conflicting properties, e.g. conductivity/permeability versus bulk modulus, the optimum is sought in a Pareto sense. Illustrative examples demonstrate the capability of the presented procedure for the design of multiphysical composites and tissue scaffolds.
ANALYSES OF INFLUENCE FACTORS ON MECHANICAL PROPERTIES OF CERAMIC COMPOSITES REINFORCED BY NANO-MICRO PARTICLES
Authors: LUO DONG-MEI , ZHOU YING-LONG , YANG HONG
Published: April 2009

The main influence factors on mechanical properties of ceramic composites reinforced by spherical nano-micro particles are investigated in this study. The sizes of the particles vary from micro (0.5 µm) to nano-scale (40 nm). Two kinds of representative volume elements (RVE) are applied to describe different arrays of nano-micro particles. One is the nesting array in which a nano-particle is nested within the microscopic particles, and the other is the enwrapping array in which a micro-particle is enwrapped by some nano-particles. The finite element (FE) analysis is conducted by the global-local homogenization method with precise period boundary conditions. The numerical simulation is performed with the changes of radius ratios of nano-micro particles, volume fractions and the interfacial properties. The results show that the effective Young's modulus of the composites with the enwrapping array has an obvious increase as compared to those with the nesting array for high volume fraction of micro-particles, and it is dependent on the radius ratios of nano-micro particles within certain volume fractions. The interfacial damage between nano-micro particles and their matrix decreases significantly the effective Young's modulus. It is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with mature interface properties.
HYDROGEN STORAGE PROPERTY OF Mg-Ni-TiO2-CNTs COMPOSITES
Authors: LI WEIXUE , HU SUMEI , HAO YUAN , DAI JIANFENG , WANG QING , XU YINGGE
Published: April 2009

In this paper, the nanocrystalling composite Mg - Ni - TiO 2- CNTs was made by mechanical ball milling under hydrogen pressure of 5.0×10-5 Pa , The hydrogen storage properties and operation temperatures were investigated. It was found that the composite can absorb 7.5wt.% hydrogen in 60s under 5.0×10-5 Pa hydrogen pressure and desorb 6.5wt% hydrogen in 600s at 260°C under 5.0×10-5 Pa hydrogen pressure. The composite has very high absorption, hydrogen capacity and remarkable kinetic properties in hydriding /dehydeiding process. TiO 2, Ni and CNTs were used as additive to improve the hydrogen storage performance. They can be utilized as an effective catalyst to improve hydriding/dehydriding performance of hydrogen storage material and lead to pronounced enhancement on the hydrogen storage property of Mg . The results showed that the composite has potential application in the future.
EFFECT OF PHBV CONTENT ON THE TRANSPARENCY AND SWELLING BEHAVIOR OF POLYMER/HECTORITE NANOCOMPOSITE HYDROGEL
Authors: ZHANG QINGSONG , ZHAO YIPING , CHEN LI
Published: April 2009

As a kind of novel biopolymer material with good biodegradability and biocompatibility, poly(β-hydroxybutyrate-co-valerate)(PHBV) was introduced into organic/inorganic network structure of nanocomposite hydrogels prepared by in-situ free-radical polymerization based on monomer N-isopropylacrylamide(NIPAM) and physical cross-linker hectorite. As viewed from appearance of the hydrogels, obvious change occurred from transparent to white with the increase of PHBV content, which reflects the structural shift from homogeneity to inhomogeneity. The swelling ratio and swelling kinetics of thermo-sensitive poly( NIPAM / PHBV /Hectorite) hydrogels with different PHBV content was investigated by gravimetric method. It was found that the incorporation of PHBV decreases the swelling ratio of pure poly( NIPAM /Hectorite) hydrogels on account of hydrophobicity of PHBV . Furthermore, in the case of swelling kinetics, the result of linear regression shows that relaxation of polymer chains of the hydrogels controls the swelling process.