bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of down-hole and laboratory shear wave velocities
Authors: Larkin T. J. , Taylor P. W.
Published: April 2009

The method of down-hole seismic surveying is described. This method was successfully used to a depth of 50 m in a cased borehole and these results are presented. The method may be used to find the in situ low strain shear modulus for use in theoretical response studies.Structural changes and changes in the stress state of samples usually result from sampling, handling, and testing procedures. Large changes in soil properties may result from these processes. An assessment of the change in soil properties is presented, which is of importance for the use of laboratory derived soil properties in theoretical in situ dynamic response studies.The magnitude of sample disturbance is assessed by comparing in situ and laboratory measured shear wave velocities. In situ down-hole shear wave velocities are compared with low strain (1 × 10−6) laboratory dynamic torsion test results. The large differences found may be correlated with the in situ shear wave velocity.A procedure is presented to correct the laboratory established shear modulus–strain relation–ship for the effects of sample disturbance. The adjusted laboratory curve is then suitable for use in theoretical response studies and will be a more accurate representation of the in situ deformation characteristics.
Cyclic strength of a sensitive clay of eastern Canada
Authors: Lee Kenneth L.
Published: April 2009

Cyclic loading tests were performed on many undisturbed specimens and a few compacted specimens of two samples of very sensitive clay from an earth dam site on the Outardes River in Quebec. Failure occurred when one or more thin shear zones developed in which the remolded soil was reduced to a liquid, while the rest of the specimen remained intact, strong, and brittle. The cyclic strength of this clay was high in comparison to that required for the foundation of a planned earth dike and was relatively strong in comparison with other clays. However, simplified analyses indicate that under some conditions dynamic loading can be expected to induce instability in this type of soil.
Measurements on a tunnel lining in very dense till
Authors: Delory F. A. , Crawford A. M. , Gibson M. E. M.
Published: April 2009

Measurements were made on a 4.3 m (14 ft) bored diameter, 3.0 m (10 ft) finished diameter tunnel for a sewer in Mississauga, Ontario. Measurements included deformation of the flexible temporary lining, pressures on the temporary and rigid concrete permanent linings, soil deformations and surface settlements as the tunnel was excavated, and the effect of the tunnel on groundwater levels.Because of the stiffness of the very dense till and the method of construction it was found that during the period of measurement the tunnel opening deformed and was largely self-supporting. Some increase of loads on the linings with time was observed, but the rate of increase was almost negligible after 6 months. The water table around the tunnel was lowered as the tunnel and the surrounding pea gravel fill acted as a drain.Indications are that the tunnel has nearly uniform all-around pressure on it, considerably less than the overburden pressure, and, therefore, that it could be considered in ring compression without bending moments in either lining. If bending moments are not present, the permanent lining could be reduced from the 460 mm (18 in.) used to half that thickness or less and still be quite conservative in supporting all-around loads equal to the overburden pressure and providing for wear.
Some aspects of road and airstrip pad design in permafrost areas
Authors: Nixon John F.
Published: April 2009

Sample analytical and numerical thermal solutions for problems involving insulated pad designs on permafrost are presented. Other aspects of pad design on permafrost are considered, including the required depth of cover for insulation subjected to different wheel loadings and the use of insulation on sloping terrain to improve pad stability.
A slope failure in till at Lebret, Saskatchewan, Canada
Authors: Sauer E. Karl
Published: April 2009

Landslides in glacial deposits are relatively rare in southern Saskatchewan, especially in till. Till is generally a very stable material so that in order for failures to occur, some stratigraphic discontinuity must exist. A landslide at Lebret, Saskatchewan, has occurred in a generally stable area. The slide has many unusual aspects to it. It is apparently taking place on a single circular surface, whereas most slides in this region are of the multiple retrogressive form with composite failure surfaces. The slide has very large dimensions compared to other slides in this area. Theaverage surface slope on the surface of the slide is relatively steep at 20°. There is no active undercutting or activity of man to cause the failure. The stratigraphy at the site does not correlate with the drift stratigraphy in the area, indicating glacial disturbance of the established stratigraphic sequénce, which would account for the fact that it is the only slide in an otherwise stable area.
Obtaining accurate pressure measurements in a stored granular medium
Authors: Jarrett N. D. , Brown C.J. , Moore D.B.
Published: April 2009

The project is concerned with the acquisition of reliable data from large-scale silos, and in particular data relating to pressures imposed on the silo by the stored material. For the purposes of the study a square plan-form steel silo was used, and the stored material was Leighton Buzzard sand. The experimental work was carried out in the environmentally controlled conditions of the laboratories at Building Research Establishment, Watford, United Kingdom. The project adopted the pressure cells designed by V. Askegaard. Both wall cells and embedded cells were used to measure pressure at the interface of the wall and stored material and within the stored material, respectively. For the embedded cells, it has been shown that the installation procedure is critical in obtaining reliable results. Preliminary tests were carried out in small-scale models until confidence in repeatability of the placement method was achieved. Even then there was some variation in results, and to ensure confidence each large-scale test was repeated five times. Pressures measured by both wall and embedded cells were compared to obtain calibration factors, and then the overall vertical equilibrium of the model was checked and found to be within the bounds of experimental error. The authors are confident of the accuracy of data which can now be achieved provided care is taken with both installation procedures and calibration checks. Key words : pressure measurement, silos, granular media, pressure cell calibration.
Leakage of dense, nonaqueous phase liquids from waste impoundments constructed in fractured rock and clay: theory and case history
Authors: Kueper Bernard H. , Haase C. Stephan , King Helen L.
Published: April 2009

This paper examines the behaviour of dense, nonaqueous phase liquids (DNAPLs) in fractured media, with an emphasis on waste-disposal ponds constructed in fractured clay and rock. Calculations are presented to estimate the height of DNAPL that may accumulate at the base of a disposal pond prior to initial entry into a water-saturated fracture. This height is found to be a function of the fluid densities, the DNAPL–water interfacial tension, the fracture aperture, and the position of the water table. A numerical model is applied to estimate the steady-state rate of DNAPL leakage from a disposal pond underlain by vertical fractures. This rate of leakage is found to be a function of the spacing of fractures, the fracture aperture, the DNAPL density, and the height of the water table in the formation outside of the impoundment. It is demonstrated that a wide range of leakage rates can occur over a relatively narrow range of parameters. A conceptual analysis of two-phase flow examines the conditions that lead to both uniform and sparse DNAPL migration pathways beneath a disposal pond in fracture networks. A case history is presented as field evidence of the concepts discussed. In particular, the case history demonstrates that sparse DNAPL migration pathways can occur in fractured rock, and that relatively low dissolved phase concentrations can exist in the immediate vicinity of DNAPL source zones. Key words : nonaqueous phase liquids, ground water, fractures, disposal ponds.
Impact of molding water content on hydraulic conductivity of compacted sand-bentonite
Authors: Haug Moir D. , Wong Lionel C.
Published: April 2009

The relationship between molding water content and hydraulic conductivity of a compacted sand-bentonite mixture was examined in a laboratory test program. This program involved triaxial permeability testing of nine specimens of 8% bentonite and Ottawa sand, compacted at standard Proctor density using molding water contents ranging from6 to 19%. The permeability tests were conducted using hydraulic gradients ranging from 19 to 40. The specimens were subjected to an average effective stress during testing of 21 kPa. The tests were conducted using continuous back pressure saturation. Each test was run for a minimum of 40 000 min (approximately 28 days) to enable the flow in and out of the specimen to come to equilibrium with respect to each other. The hydraulic conductivity decreased from 6.5 × 10−9 cm/s for a molding water content of 5.9% to 1.4 × 10−9 cm/s for a molding water content of 15.8%. However, although the hydraulic conductivity was related to the molding water content, the variation in hydraulic conductivity was relatively small. Therefore, the low values reported for all hydraulic conductivity tests suggest that molding water content is not a critical design factor in the construction of a low-permeability sand-bentonite liner. Key words : molding water content, bentonite, liners, hydraulic conductivity, triaxial permeability testing, covers, sand.
Cracking in drying soils
Authors: Morris Peter H. , Graham J. , Williams David J.
Published: April 2009

Cracking in soils that are undergoing drying is controlled by soil suctions and by soil properties such as compression modulus, Poisson's ratio, shear strength, tensile strength, and specific surface energy. The paper reviews the occurrence and morphology of cracks in dry-climate regions of Australia and Canada. After reviewing the behaviour of unsaturated soils and the mechanics of cracking, solutions are developed based on (i) elasticity theory, (ii) the transition between tensile and shear failure, and (iii) linear elastic fracture mechanics. The solutions are compared and related to crack depths observed in the field. Key words : clay, cracks, crust, shear strength, soil suction, tensile strength, unsaturated soil, weathering.
Compaction of dune sand backfill by concrete shaft vibrators
Authors: Mirza S. Idris
Published: April 2009

Backfilling is a time-consuming operation at any construction project. Because of construction constraints and to minimize excavation and backfilling costs, utility trenches are made as narrow as practicable, which precludes the use of large compactors. The backfill is therefore placed in thin layers and compacted with hand compactors, making backfilling a slow operation. This paper presents the details of development of a fast, effective, and reliable backfill compaction procedure. This method is based on the concept that the sand being a cohesionless material can be easily densified under its own weight by mere vibrations if the intergranular friction between the sand particles is reduced. The method allows placement of saturated dune sand backfill in lifts up to 1 m in thickness, and the compaction is achieved by vibrating the mass by inserting concrete shaft vibrators on a regular grid pattern. The results and analysis of numerous laboratory experiments and 13 full-scale field test trials which form the basis of this compaction technique are also included in this paper. Key words : backfilling, dune sand, intergranular friction, vibrations, concrete shaft vibrators.
The adhesion factor: applications and limitations
Authors: Sladen J. A.
Published: April 2009

The conventional concept of an empirical adhesion factor that relates undrained shear strength of a clay soil to ultimate shaft friction can be shown to have a theoretical basis for vertical piles, even though conditions at the interface are fully drained. The adhesion factor approach and the effective stress approach for shaft resistance are in fact consistent. This is because horizontal stress at the interface and undrained shear strength are both influenced by the same factors. The general implication of the conventional approach that the mechanism is undrained and that the mobilized shear resistance between a structure and clay is a fraction of the undrained soil shear strength is, however, incorrect. This concept can lead to significant errors if it is extrapolated to situations, for which the empirical data were not derived, such as beneath gravity structures on clay foundations, where effective stress normal to the interface is independent of soil undrained shear strength. Key words : piles, clay, adhesion, shaft friction.
LONG-RANGE ORDER IN TWO-DIMENSIONAL XXZ MODEL
Authors: YOU WEN-LONG
Published: April 2009

In the present paper, by applying the reflection positivity method due to Dyson, Lieb, and Simon, we rigorously establish the sufficient condition for existence of the Néel long-range order (NLRO) in two-dimensional spin-1/2 XXZ. Our result shows that if the anisotropic coupling Δ satisfies 0 ≤ Δ ≤ 0.30 or Δ ≥ 1.52, the existence of the NLRO along easy axis is proved.
ENTANGLEMENT OF A GENERAL FORMALISM Ξ-TYPE THREE-LEVEL ATOM INTERACTING WITH A SINGLE-MODE FIELD IN THE PRESENCE OF NONLINEARITIES
Authors: OBADA A.-S. F. , EIED A. A. , ABD AL-KADER G. M.
Published: April 2009

We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of a Ξ-configuration three-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system, we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent or binomial state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy are analyzed.
THE EFFECT OF Y ON THE OXIDATION OF Mg-Zn-Zr ALLOYS
Authors: NING ZHILIANG , LIANG WEIZHONG , CAO FUYANG , SUN JANFEI
Published: April 2009

The effects of Y addition up to 5.13% (in weight) to Mg - Zn - Zr alloys on oxidation behaviors under atmospheric ambient conditions were investigated in this study. Samples were heated in the ambient atmosphere at 400°C, with samples cooled to room temperature for mass measurement after some period time of cumulative exposure to obtain kinetic curves. XRD is used to analyze the mixture of oxides. Scanning electron microscopy combined with energy dispersive spectroscopy was used to study the scale microstructure and to obtain composition-depth profiles through the oxide layers. The oxidation results show that the weight gains for the alloys containing low Y concentration are obvious. The oxide films are thick and porous on the alloys containing low Y and thin and protective on alloys containing relatively high Y concentration. The addition of Y into Mg - Zn - Zr alloys results in the formation of protective film which is resistant to oxidation.
THE EFFECTS OF COLD EXTRUSION ON GRAIN SIZE REFINEMENT AND PLASTICITY FOR MAGNESIUM ALLOY
Authors: Yu Yang , Wang Erde
Published: April 2009

It is well-known that the plasticity of magnesium and magnesium alloy is too low to be processed at low temperature. After normal hot extrusion, the plasticity of magnesium alloy can be improved, but not noticeably. In this paper, cold extrusion of commercial AZ31 magnesium alloy with severe plastic deformation was performed at room temperature with various extrusion ratios from 2:1 to 12.5:1 in order to refine the grain size of AZ31 magnesium alloy. Finally the grain size between 2~3 µm was obtained. And the influence of different grain size on the plasticity was further investigated. And the elongation of the initial billet with the grain size of 300 µm whose elongation is about 10.4%. After extrusion at room temperature with different extrusion ratios, the average grain size can be refined to below 10 µm, and the plasticity increased to 24%~30%. In order to study the effect of plasticity of AZ31 magnesium alloy under different processing techniques, we study the correspondence between plasticity and crystalline size at the same time. All results proved that, the increase in elongation could be mainly attributed to refining of the grain size of the magnesium crystalline. It also showed that, when the average grain size of AZ31 magnesium alloy was below 5 µm, the plasticity increased noticeably by cold extrusion.
INVESTIGATION ON TOOL WEAR RATE FOR MODIFIED AND UNMODIFIED ALUMINIUM-SILICON CASTING ALLOY
Authors: HAQUE M. M. , KHAN A. A. , ISMAIL AHMAD F.
Published: April 2009

This study demonstrates and explains the effect of strontium modification on machinability of aluminium-silicon eutectic (LM-6 type) alloy. This alloy is known to have many favourable features including weight to strength ratio, high corrosion resistance and excellent castability. However, normal unmodified LM-6 alloy has poor machinability, which reduces its applications range. In this work, various samples of LM-6 alloy were cast using sand and metallic chill mould with and without strontium addition. Machining on each cast product, was carried out using recommended cutting parameters for Al - Si alloys. Strontium modified samples have recorded a reduction in average flank wear, an increase in shear plane angles and a reduction in chip thickness. The main reason for this improvement is the refining effect of strontium, which reduces the size of the hard silicon particles. As a result, their abrasive action on the tool face has reduced a lot. Dramatic reductions in tool wear rate were recorded when the microstructures were refined. On the other hand, when no refinement of microstructure occurs, tool wear rate becomes high. Chip analysis showed that strontium modified sample produced a thinner chip thickness with a larger shear plane angle, requiring less cutting forces. The tool wear depends not only on the phases present in the work material, but also on their sizes and distribution over entire structure. Thus, strontium modification has better effect on machinability of die cast alloy compared to that of the sand cast LM-6 alloy.
MODIFICATION OF Mg2Si MORPHOLOGY IN A Mg-3Si-3Sn ALLOY DURING ISOTHERMAL HEAT TREATMENT
Authors: XIAO LIU , LI XINLIN , WANG XiANG , MA GUO RUI , FENG DAN
Published: April 2009

The effects of different isothermal holding temperatures and times on the morphology of Chinese script shaped or fibriform eutectic Mg 2 Si phases in a Mg -3 Si -3 Sn alloy were investigated during isothermal heat treatment. With increasing heat treatment temperature, the spheroidizing time for the coarse eutectic Mg 2 Si phases is reduced dramatically. After isothermal heat treatment of 2 h at 550°C, the morphology of the eutectic Mg 2 Si transforms completely from the coarse Chinese script type and fibriform shape into fine, spherical shape with the lowest interface energies. The spheroidizing mechanism of the Chinese script shaped or fibriform eutectic Mg 2 Si particles seems to be attributed to the 'Rayleigh shape instability'.
VISCOSITY OF LIQUID ALUMINIUM MODIFIED BY ELECTRIC PULSE
Authors: QI JINGANG , WANG JIANZHONG , WANG BING , CANG DAQIANG
Published: April 2009

The modification of liquid metal by electric pulse (EP) is a novel method for grain refinement. In this work, based on the reported structural heredity of EP-modified liquid aluminum, we investigated its viscosity change by using torsional oscillation viscometer. The results validate the viscosity of EP-modified liquid aluminum also decreases with increasing temperature and meets approximately exponential correlation on the whole. Moreover, it is especially important that the EP-modified liquid aluminum has the higher viscosity and possesses the bigger viscous-flow cluster in a certain temperature range, which should be associated with the increase of the order degree of its liquid structure. Differential scanning calorimetry (DSC) measurement also confirms that viewpoint. These coupling results experimentally testify the proposed mechanism of electric pulse modification (EPM) modeled merely by postulation.
THE EFFECT OF RRA ON THE MICROSTRUCTURE AND PROPERTIES OF A NOVEL Al-Zn-Mg-Cu-Zr ALLOY
Authors: LI XIWU , XIONG BAIQING , ZHANG YONGAN , ZHU BAOHONG , LIU HONGWEI , LI ZHIHUI
Published: April 2009

A novel Al -7.5 Zn -1.6 Mg -1.4 Cu -0.12 Zr alloy was subjected to the retrogression and re-ageing (RRA) treatments at a lower range of retrogression temperatures from 170 to 200°C. The effect of RRA on the mechanical properties, electrical conductivity and the microstructure of the alloy has been investigated. The results indicate that an increase in the yield strength of the alloy can be achieved after RRA treatment. With increase of the retrogression temperature, the retrogression time for keeping the strength levels similar to T6 temper decreases rapidly. When submitted to RRA at 170°C for 90-120 min, the alloy can obtain a good performance on both SCC and mechanical strength; the electrical conductivity was above 40%IACS, reaching values typical for T76 condition and the tensile yield strength values were 552-570 MPa which is higher than that of the T6 temper. The microstructure is a very fine distribution of GP zones and η′ precipitates inside grains, similar to T6 condition and η precipitates on grain boundaries distributed similarly to T7 temper.
MICROSTRUCTURAL EVOLUTION AND MECHANICAL PROERTIES OF Ti-(Ni, Fe)-Sn ULTRAFINE EUTECTIC ALLOYS
Authors: PI DONG HYOUK , KIM KI BUEM , PARK JIN MAN , HAN JUN HEE , KIM DO HYANG
Published: April 2009

Ultrafine eutectic alloys have been developed in Ti - Ni , Ti - Fe and Ti -( Ni , Fe )- Sn alloys. The Ti 76 Ni 24 and ( Ti 74 Ni 26)97 Sn 3 ultrafine eutectic alloys consist of a mixture of α- Ti and Ti 2 Ni phases, and β- Ti ( Sn ) and Ti 2 Ni phases, respectively, whereas the Ti 70.5 Fe 29.5 and ( Ti 70.5 Fe 29.5)97 Sn 3 alloys are composed by a mixture of β- Ti ( Sn ) and FeTi phases with relatively spherical colony. The compression tests of Ti 76 Ni 24, ( Ti 74 Ni 26)97 Sn 3 and Ti 70.5 Fe 29.5 ultrafine eutectic alloys reveal a strength of 1400 ~ 1800 MPa with very limited plastic strain of 0.1 ~ 1%. On the contrary, a ( Ti 70.5 Fe 29.5)97 Sn 3 alloy exhibits high strength of 2270 MPa with enhanced plastic strain of 3.1%. Based on these results, it is feasible to suggest that the eutectic morphology and interfacial coherency between the Ti solid solution and intermetallic phases influence to control the macroscopic plasticity of the Ti - Ni and Ti - Fe ultrafine eutectic alloys.
STUDY ON FABRICATION OF SHAPED AL ALLOY FOAM BY TWO-STEP FOAMING METHOD
Authors: CHU XUMING , WANG HUI , HE SIYUAN , HE DEPING
Published: April 2009

In this study, a novel method two-step foaming method (TSFM) has been proposed to fabricate Al alloy foams with irregular shapes. The two steps Al alloy foaming process and cell-structures evolution have been investigated experimentally. The relationship between foamable precursor, foaming parameters and cell-structures of the final foam samples has been observed. Moreover, the Al foam samples with regular and irregular shapes prepared by TSFM are shown in this paper.
INFLUENCE OF T5 TREATMENT ON MICROSTRUCTURE AND PROPERTIES OF EXTRUDED ZK60 MAGNESIUM ALLOY
Authors: ZHANG ZHIMIN , ZHANG BAOHONG
Published: April 2009

As-cast ZK60 magnesium alloy that has been treated by homogenizing was forward extruded at 380°C and different extrusion ratios. Half of the extruded samples were treated by T5 treatment (10 hours at 170°C). The microstructure and mechanical properties of extruded samples that have been treated by T5 treatment and not been treated by T5 treatment have been measured. Experimental results show that the T5 treatment of extruded ZK60 magnesium alloy will cause the tensile strength and hardness to increase in some sort, the yield strength to increase obviously, but elongation to decrease slightly. When ZK60 magnesium alloy is extruded at 380°C, the second phase, MgZn and a small quantity of MnZn 2, will precipitate, and the distribution of second phase is even and dispersed. After T5 treatment, the change of grain size is not obvious, but the quantity of precipitated phase obviously increases comparing with extruded samples, and some of the precipitated phase aggregate and grow.
NANOSTRUCTURED ALUMINA CERAMIC MEMBRANES FOR GAS SEPARATION
Authors: BROWN IAN , BOWDEN MARK , KEMMITT TIM , WU JEREMY , CARVALHO JULES
Published: April 2009

Nanostructured alumina ceramic templates have been fabricated by anodizing annealed high-purity aluminium foil. Pore diameter, pore separation and thickness in these alumina ceramics can be controlled using a range of acid electrolytes and anodizing voltage profiles. Thermal development of the structure of these robust and optically clear templates have been compared using XRD, thermal analysis and 27 Al MAS NMR techniques, showing that species substituted in the alumina lattice from decomposition of the acid electrolyte play a major role in determining the chemical and physical stability of the ceramic template at elevated temperatures. Deposition of ultrathin palladium films on the surface of these alumina templates creates robust membranes that enable hydrogen separation from mixed gas streams at elevated temperatures. Gas permeability measurements through these membranes as a function of temperature have demonstrated their very high selectivity for hydrogen.
EFFECTS OF V2O5 ADDITION ON MICROWAVE DIELECTRIC PROPERTIES OF 16CaO-9Li2O-12Sm2O3-63TiO2 CERAMICS
Authors: GU YONGJUN , HUANG JINLIANG , SUN DAOMING , LI QIAN , WANG XIAO , XU HUI
Published: April 2009

Effects of V 2 O 5 addition on the microwave dielectric properties of 16 CaO -9 Li 2 O -12 Sm 2 O 3-63 TiO 2 (abbreviated CLST) ceramics prepared by conventional mixed oxides method were investigated as a function of V 2 O 5 content and sintering temperature. All the specimens were sintered between 1100°C and 1250°C. The sintering temperature of the CLST ceramics was lowered by 100°C with V 2 O 5 addition. With the changing content of V 2 O 5, the dielectric constants lie between 88.6 and 108.2, while the Q × f values are between 3275 and 6573 GHz. Especially, the specimens doped by 0.75 wt% V 2 O 5 sintered at 1200°C and 1250°C for 3 h show good microwave dielectric properties with Kr =100.4-108.2, Q × f >4500 GHz , and TCF=7-8 ppm/°C. Obviously, V 2 O 5 could be used as a suitable sintering aid that could improve densification and microwave dielectric properties of the CLST ceramics.
EFFECT OF Al ON MICROSTRUCTURE AND PROPERTIES OF In718 ALLOY
Authors: LIU FANG , YANG SHULIN , SUN WENRU , GUO SHOUREN , HU ZHUANGQI
Published: April 2009

Compared with the conventional In 718 alloy, the addition of Al at the level of 1.24% and 1.50% greatly increases the precipitation of γ′ phase and the compact form of γ″/γ′/γ″ structure, which has been demonstrated in previous studies. The δ phase precipitation at the grain boundaries is noticeably suppressed. Large amount of Laves phase (( Fe , Ni , Cr )2( Nb , Mo )), small amount of M 7 C 3 carbide and σ phase (( Fe , Ni )( Cr , Mo , Nb )) are precipitated at the grain boundaries. After aging at 680°C, the grain boundary precipitates are increased significantly. Large amount needle-like σ phase is precipitated at the grain boundary in the alloy with 1.50% Al . After aging at 680°C for 1000h, the grain boundary precipitates are worsened further, but the coarsening of the compact form γ″/γ′/γ″ is lighter than the γ″ phase in the normal In 718 alloy.

The tensile strength at room temperature and 680°C are increased due to Al increasing. While the tensile ductility and impact toughness of the alloy decrease significantly, and a sharp decrease has been found during the long term aging at 680°C.

The mechanism by which Al influencing the microstructure and mechanical properties of In 718 alloy is to be discussed.
INTEGRALLY DIRECTIONALLY SOLIDIFIED MICROSTRUCTURE OF AN NIOBIUM SILICIDE BASED ULTRAHIGH TEMPERATURE ALLOY
Authors: GUO XIPING , GUO HAISHENG , YAO CHENGFANG , GUAN PING
Published: April 2009

Integrally directional solidification of an advanced Nb silicide based ultrahigh temperature alloy was conducted with the use of special ceramic crucibles. The melt temperature was 2000°C and the withdrawing rate was respectively 5, 10, 15, 30, 50, 80 and 100 µm/s. The directionally solidified microstructure was composed of primary ( Nb ,X)5 Si 3 rods and ( Nb , Ti ) ss + ( Nb ,X)5 Si 3 eutectic colonies (here X represents Ti and Hf elements) that distributed evenly and aligned erectly along the growth direction. The quenched solid/liquid (S/L) interfaces had the morphology of a series of protruded parallel eutectic cells along the growth direction. ( Nb , Ti ) ss and ( Nb ,X)5 Si 3 slices grew in a coupled manner in each eutectic cell, forming a typical lamellar eutectic morphology. Both the average diameter of eutectic cells and lamellar spacing in them decreased with the increase of withdrawing rates. The solidification path was that primary ( Nb ,X)5 Si 3 rods formed firstly and then the retained liquid around solidified into ( Nb , Ti ) ss + ( Nb ,X)5 Si 3 eutectic cells.
DISTRIBUTION AND CORROSION BEHAVIORS OF THE TRIPLE JUNCTIONS IN A GRAIN BOUNDARY ENGINEERED 304 STAINLESS STEEL
Authors: FANG XIAOYING , WANG WEIGUO , GUO HONG , QIN CONGXIANG , ZHOU BANGXIN
Published: April 2009

Grain boundary character distribution (GBCD) and triple junction character distribution (TJCD) in a 304 stainless steel cold rolled with the thickness reduction of 6% and then annealed at 1323K for 5 minutes(GBE process) were analyzed by electron back scatter diffraction (EBSD). The intergranular corrosion (IGC) resistance of various triple junctions and grain boundaries were evaluated after sensitization treatment at 1073K for 30 minutes. The results showed special TJ containing 2 or 3 CSL boundaries exhibit higher resistance to IGC than other TJs. In addition, the {411} and {221} symmetrical tilt grain boundaries (STGBs) are more resistant to intergranular corrosion for Σ9 boundaries.
FRICTION STIR PROCESSING OF SKD61 TOOL STEEL
Authors: CHEN YINGCHUN , NAKATA KAZUHIRO
Published: April 2009

In this study, SKD61 tool steel was friction stir processed (FSP) using a polycrystalline cubic boron nitride (PCBN) tool. Microstructure evolution and mechanical property in FSP zone were investigated. Microstructural observation results showed that the microstructures in FSP zone surface were fine grains in the range of 1 - 4 μm due to large plastic deformation during FSP. Micro-hardness test results showed that the average hardness value in FSP zone was 773 HV, 3.7 times the hardness in base metal (210 HV). The wear test results showed that FSP surface showed a significantly lower wear rate than that of the base material at all loads. The relation between microstructural evolution and mechanical property in FSP zone was discussed.
THE Z-PHASE IN 9Cr FERRITIC/MARTENSITIC HEAT RESISTANT STEEL
Authors: YIN FENGSHI , CHEN FUXIA , JIANG XUEBO , XUE BING , ZHOU LI , JUNG WOOSANG
Published: April 2009

The precipitation behavior of Z -phase was investigated during long-term aging at 650°C in an ultra low carbon 9 Cr ferritic/martensitic heat resistant steel. The steel was prepared by vacuum induction melting followed by hot forging and rolling into a plate. The plate was normalized at 1100°C for 1h, cooled in air and tempered at 700°C for 1h. Bimodal nano-sized MX precipitates distribute densely and homogeneously in the matrix within martensitic lath after normalizing-and-tempering heat treatment. After aging at 650°C for 1200h, the Z -phase was found to nucleate on the larger nano-sized MX. The Z -phase and MX have the following orientation relationship: <112> Z - phase //<001> MX and [Formula: see text].
APPLICATION OF ANN BACK-PROPAGATION FOR FRACTURE TOUGHNESS IN MICROALLOY STEEL
Authors: DUAN HONGYAN , LI YOUTANG , HE GUIPING , ZHANG JIN
Published: April 2009

Artificial neural network (ANN) back-propagation model was developed to predict the behavior of fracture toughness and tensile strength as a function of microstructure. Both fracture toughness and tensile strength were found to increase with the increase in martensite content in a dual phase microstructure of microalloy steel. The primary objective of the ANN Back-propagation (BP) prediction model was to validate and extend the application of microalloy steels for various engineering applications. The ANN training model has been used to predict the optimum toughness properties in terms of intercritical annealing temperature and martensite content. This can be used as a practical tool for predicting the fracture toughness in other series of steels comprising dual-phase microstructures and also to optimize strength and ductility properties. The ANN model exhibited excellent comparison with the experimental results. It is concluded that predicted fracture toughness by the trained neural network model seem more reasonable compared to approximate methods. It is possible to claim that, ANN is fairly promising prediction technique if properly used. Training ANN model was introduced at first. And then the neural network architecture is designed. The performance of system is summarized at last. In order to facilitate the comparisons of predicted values, the error evaluation and mean relative error are obtained. The result show that the training model has good performance, and the experimental data and predicted data from ANN are in good coherence.
CHARACTERIZATION OF SHEAR BANDS IN TWO BULK METALLIC GLASSES WITH DIFFERENT INHERENT PLASTICITY
Authors: GU JIANSHENG , LI LEI , ZHANG TAIHUA , JIANG PENG , WEI BINGCHEN , SUN ZHIWEI
Published: April 2009

Shear banding characterization of Zr 64.13 Cu 15.75 Ni 10.12 Al 10 and Zr 65 Cu 15 Ni 10 Al 10 bulk metallic glasses (BMGs) with significant difference in inherent plasticity and quite similar chemical composition was studied by depth sensitive macroindentaion tests with conical indenter. Well-developed shear band pattern can be found for both BMGs after indentation. Distinct difference in the shear band spacing, scale of plastic deformation region and the shear band branching in the two BMGs account for the different plasticity.
PRELIMINARY STUDY OF FABRICATING BULK FE-BASED AMORPHOUS ALLOY BY COLD GAS DYNAMIC SPRAYING
Authors: GUAN LEDING , YAN BIAO , LONG LING , YANG SHA
Published: April 2009

Cold gas dynamic spraying (CGDS) technique makes use of high-speed gas current to spray diversified metal, alloy and composite materials under room temperature or with a little heated. It is one kind of novel surface engineering technologies, aimed at eliminating such negative influences as oxidation, gasification, melt, crystallization and gas decomposition and so on existing in hot spraying technologies. Due to its peculiar characteristics such as low spraying temperature, non-oxidation, low stress among coating layers, compactification, and high utilization rate of raw materials, as well as effective applications in the domain of fabricating coatings, the CGDS technique has attracted great attention. As it has the advantages aforementioned, especially avoiding the changes of material properties resulted from high spraying temperature, CGDS provides a kind of revolutionary means for fabricating such heat-sensitive materials as amorphous alloys. The paper reviews the current situation and application development of the CGDS technique, and presents our preliminary exploration of fabricating bulk Fe -based amorphous alloy via CGDS together with mechanical milling process.
NOVEL POLYMER ELECTROLYTE BASED ON POLY(VINYLIDENE FLUORIDE) AND POLY(4-VINYL PYRIDINE) HAVING A NANO-CHANNEL FOR ION TRANSPORTATION
Authors: OH SEUNG HYUN , KANG SEONG LAK , JEONG KWANG-UN , NAH CHANGWOON , CHO BAIK-HWAN
Published: April 2009

The micro-porous polymer electrolytes membranes(PEMs), notably electro-spun fiber mats, have been suggested to give an improved ionic conductivity. However, the mat-type PEMs have a poor mechanical and dimensional stability because of their inevitable porous nature. In this study, we suggest a new PEM system based on poly(vinylidene fluoride)(PVdF) mats, which can overwhelm such shortcomings of the porous mats by introducing another component, poly(4-vinyl pyridine)(P4VP), into the mats. The tensile strength of PVdF / P 4 VP membrane was considerably improved compared with that of pristine PVdF membrane under dry and wet conditions. The ionic conductivity was also improved by about 10 times than that of PVdF mat. A micro- to nano-size gap was formed at the interfaces between PVdF nanofiber and P 4 VP , and this may act as a channel for fast ion transportation under wet condition.
MECHANICAL PROPERTIES AND FRACTURE BEHAVIOR OF ELECTROLESS NI-PLATED SHORT CARBON FIBER REINFORCED GEOPOLYMER MATRIX COMPOSITES
Authors: LIN TIESONG , JIA DECHANG
Published: April 2009

Electroless Ni -plated short carbon fiber reinforced geopolymer matrix composites with various carbon fiber/matrix interface coating thicknesses have been successfully fabricated. The influences of coating thickness on the mechanical properties and fracture behavior have been investigated by three-point bending test and scanning electron microscopy. The flexural strength and Young's modulus of Ni -plated short carbon fiber reinforced geopolymer composites exhibit maximums as the average fiber coating thickness increases, but the work of fracture has a sharp decrease, and the fracture manner changes from ductile to brittle. This is mainly attributed to the fact that the carbon fibers favor breakage rather than pulling-out during loading because of the higher interface bonding strength of fiber/matrix, and pliability of the carbon fibers decreases with the increase of the coating thickness.
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HYPEREUTECTIC Al-Si/AlNp COMPOSITE
Authors: PARK SEULKI , CHOI JINMYUNG , PARK BONGGYU , PARK IKMIN , PARK YONGHO , KIM YONGJIN
Published: April 2009

Hypereutectic Al - Si alloys with fine and evenly distributed Si precipitates have superior mechanical properties In this study, hypereutectic Al - Si alloy powders which contained 15 and 20wt% Si were prepared by a gas atomization process. 1, 3 and 5wt% AlN particles were blended with the Al - Si alloy powders using turbular mixer. The mixture was consolidated by Hot Press at 550°C for 1h under 60MPa. Relative density of the sintered samples was about 98% of theoretical density. This study was investigated by two ways. One is the effect of reinforcement weight fraction and the other is the effect of Silicon contents on the mechanical properties of the composite. Microstructural characterization and phase evaluation were carried out using X-ray Diffraction, Scanning Electron Microscopy equipped with Energy Dispersive Spectrometer. The results showed that the smaller the reinforcement particle size was and the better its distribution was, the higher ultimate tensile strength and hardness were.
EFFECT OF ZIRCONIUM ADDITION ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF TiC/Ti6A14V COMPOSITES
Authors: MA XULIANG , WANG XIANG , LI LI , GAI PENGTAO , ZHU CHENGWU
Published: April 2009

TiC/Ti6A14V composites with different Zr additions were prepared successfully in a consumable vacuum arc furnace equipped with a water-cooled copper crucible and the effect of the Zr content on the microstructure and mechanical property of 15 vol.% TiC/Ti6A14V composites was investigated by XRD, SEM and hardness testing. The results show that when the level of Zr addition is less than 4 wt.%, the morphology of the primary TiC in the composites is dendrite, and the petal-shape, piece-shape or palpus-shape eutectic TiC separates out around the primary TiC . The average size of the primary TiC decreases and the amount of eutectic TiC increases gradually with increasing Zr content. The effects of Zr on morphology of the primary TiC weaken with further addition of Zr . And the hardness (HRC) of composites was obviously increased in the whole range of Zr addition. The refinement mechanism of Zr was attributed to the combined effects of increase in nucleation rate at the constitutionally supercooled zone ahead of the solidification front and reduction in growth rate.
TRIBOLOGICAL PROPERTIES OF Ti(Al,O)/Al2O3 COMPOSITE COATING BY THERMAL SPRAYING
Authors: SALMAN ASMA , GABBITAS BRIAN , CAO PENG , ZHANG DELIANG
Published: April 2009

The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti ( Al , O )/ Al 2 O 3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion.

A feedstock of Ti ( Al , O )/ Al 2 O 3 composite powder was produced from a mixture of Al and TiO 2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating.

The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.
FUNCTIONALIZED MWCNTS REINFORCED POLYETEHYLENE FIBER COMPOSITE: MECHANICAL STRENGTH CHARACTERIZATION
Authors: SULONG A. B. , MUHAMAD N. , GHAZALI M. J. , JAHARAH A. G. , TAN SOON HUAT , PARK J. H.
Published: April 2009

This article studies about the mechanical strength of different functionalized Carbon nanotubes (CNTs) reinforced Polyethylene (PE) fiber composite fabricated by melt spinning. There are four types of CNTs used, which are called as produced, carboxylated, octadecylated, polymer wrapped CNTs . Influence of mechanical drawing (melt spinning) on the mechanical strength of fibers is measured by direct comparison with mechanical strength of bulk type functionalized CNTs polymer composites, which fabricated using hot press. Dispersion and interfacial bonding strength/adhesion of CNTs with PE matrix are investigated through fracture surfaces image analysis. Functionalized CNTs composites show a significant improvement of mechanical strength of pure polymer than non functionalized CNTs polymer composite. Whereas polymer wrapped CNTs polymer composite give the highest mechanical strength in this study. Mechanical strength of bulk composites are significantly increased after mechanical drawing process indicates that melts spinning may influence on the crystallization of polymer. Fracture surface analysis revealed that additional functionalized CNTs enhanced dispersion and interfacial bonding with polymer matrix.
MICROSTRUCTURE AND PROPERTIES OF IN SITU SYNTHESIZED ZrC-ZrB2/Fe COMPOSITE COATING PRODUCED BY GTAW
Authors: WANG ZHENTING , CHEN LILI , ZHANG XIANYOU
Published: April 2009

A metal matrix composite coating reinforced by ZrC - ZrB 2 particulates has been successfully fabricated utilizing the in situ reaction of Zr , B 4 C and Fe pre-placed mixed powders by gas tungsten arc welding (GTAW) cladding process. Various volume fraction of ZrC - ZrB 2 particulates composite coatings were produced through cladding different weight ratios of Zr + B 4 C (30%, 50%, 70%) to improve the wear resistance of AISI1020 steel substrate. The Microstructure of the coating was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrum (EDS), meantime microhardness and wear resistance at room temperature of the composite coating were examined by means of Microhardness Tester and Wear Tester, respectively. The results show that the main phases of the composite coating obtained by GTAW are ZrC , ZrB 2 and α- Fe , ZrC exhibits hexahedron and petal shapes, ZrC - ZrB 2 compound presents acicular and clubbed forms. With the increase of content of Zr + B 4 C , the maximum volume fraction of ZrC - ZrB 2 particulates can reach 16.5%, microhardness is up to 1300HV, and wear resistance is about twenty times higher than that of AISI1020 steel substrate.
EFFECT OF SINTERING TEPMERATURE ON MICROSTRUCTURE OF Ti6Al4V MATRIX COMPOSITES
Authors: HUANG LUJUN , YANG FUYAO , GUO YONGLIANG , ZHANG JIE , GENG LIN
Published: April 2009

( TiBw + TiCp )/ Ti 6 Al 4 V composites were fabricated by reactive hot-pressing at the temperature range of 800~1200°C using the starting materials of TiB 2, C and Ti 6 Al 4 V powders. The XRD results suggested that the reaction between C and Ti happened 900°C and above, while the reaction between TiB 2 and Ti happen at 1100°C and above. SEM results also suggested that the reaction between C and Ti was prior to that between TiB 2 and Ti . With the increase of the sintering temperature, the size of TiC particle and TiB whisker reinforcements increased gradually. The TiC particle was formed at the boundaries of original Ti 6 Al 4 V particles, while the TiB whiskers grew toward the inside of Ti 6 Al 4 V particles, which resulted in a strong bonding between neighboring Ti 6 Al 4 V particles. The results of hardness and relative density tests showed that the ( TiBw + TiCp )/ Ti 6 Al 4 V composites sintered at 1100°C had the highest hardness and relative density compared with that sintered at other temperatures.
MECHANICAL PROPERTIES OF IN-SITUFeAl-TiB2 INTERMETALLIC MATRIX COMPOSITES
Authors: KIM JONGHOON , PARK BONGGYU , PARK YONGHO , PARK IKMIN , LEE HEESOO
Published: April 2009

Intermetallic matrix composites reinforced with ceramic particles have received a great deal of attention. Iron aluminide is known to be a good material for the matrix in such composites. Two processes were used to fabricate FeAl - TiB 2 intermetallic matrix composites. One was liquid melt in-situ mixing, and the other was arc melting and suction casting processes. FeAl - TiB 2 IMCs obtained by two different methods were investigated to elucidate the influence of TiB 2 content. In both methods, the grain size in the FeAl alloy decreased with the presence of titanium diboride. The grain size of in-situ FeAl - TiB 2 IMCs became smaller than that of arc FeAl - TiB 2 IMCs. Significant increase in fracture stress and hardness was achieved in the composites. The in-situ process gives clean, contamination-free matrix/reinforcement interface which maintained good bonding causing high load bearing capability. This contributed to the increase in the mechanical properties of composites.