bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of a Small Volume Liquid Phase on the Hot Deformation in the BaPbO3/2024Al Composite
Authors: Fan Guo Hua , Zheng Zhen Zhu , Pang Jin Cheng , Geng Lin
Published: June 2010

In this paper, BaPbO3(5Vol.%)/2024Al composite was fabricated by powder metallurgy method. Nanosized Pb particles were formed from the in-situ reaction between BaPbO3 and 2024Al, and mainly distributed homogeneously inside grains. The hot compression deformation of the composite at different temperatures was performed. The microstructure evolution of the 2024Al matrix and dynamic mechanical analysis (DMA) of the composite were made to investigate the effect of liquid Pb on the hot deformation. The results show that the presence of the liquid phase reduces deformation resistance by decreasing dislocation pileups, and simultaneous decrease in Young’s modulus of the composite.
Interfacial Characteristics of WC Particles Reinforced Hadfield Steel Matrix Composites
Authors: Zhang Guo Shang , Gao Yi Min , Xing Jian Dong , Wei Shi Zhong , Li Ji Wen , Xu Liu Jie
Published: June 2010

In order to improve the wear resistant properties, WC ceramic particles were used to reinforce Hadfield steel. WCp/Hadfield steel composites were fabricated by optimized solid state sintering process of powder metallurgy. Interface structure, constituent phase and the forming mechanism of the composites were investigated systematically. The results show that the WCp/Hadfield steel composites have uniformly distributed particles and well bonded interface between WC particles and Hadfield steel. In the WCp/Hadfield steel composites, the interface between WC particles and Hadfield steel matrix is of shell shape, in which W, Fe and Mn elements diffuse between the two phases. The interface is of metallurgical bond, in which a new phase, namely Fe3W3C is formed. The micro-hardness of the interface layer is between those of WC and the steel matrix, which can provide a guarantee for the property transition between WC particles and Hadfield steel matrix. The diffusion reaction mechanism of the interface was also systematically studied.
Effectiveness of Residual Stress on Forming Copper Patterns of Printed Circuit Board
Authors: Lee Hyo Soo , Kwon Hyouk Chon
Published: June 2010

The effectiveness of residual stress on forming copper patterns of printed circuit board was investigated during applied thermal conditions. Generally, the electrolytic copper foil showed a compressive residual stress about -54MPa as received, which easily caused to form copper patterns irregularly. We verified the compressive residual stress was relaxed with applying thermal conditions under 200°C for a few hours. And also, we observed that the compressive residual stress of copper foil tended to be relaxed, constant, and compressive again during heating times at each temperature. The relationships between residual stress and etching factor of copper pattern were analyzed in this works.
Effects of Cu Powder Size on the Microstructure of TiB2/Cu Composites Fabricated by Reactive Infiltration Process
Authors: Kato Shinji , Kobashi Makoto , Kanetake Naoyuki
Published: June 2010

Recently, industrial technology for both improving thermal conductivity and controlling the coefficient of thermal expansion of heat sink materials has became an important issuebecause of the downsizing of electronic devices. We have been investigating the innovative processing method for TiB2 dispersed Cu matrix composite by reactive infiltration process in which the combustion reaction of elemental powders (Ti+2B+Cu → TiB2+Cu) and pressureless infiltration of molten Cu into porous reaction product (TiB2/Cu composite) are combined. By this process, fine TiB2particles (2~3µm) can be dispersed in Cu matrix homogeneously. However, for better thermal conductivity and reduced thermal expansion, 3-dimentionally continuous inter-penetrating structure of TiB2 and Cu phases is suitable. In this study, we researched the effects of Cu powder size and volume fraction in Ti,B,Cu green powder compact on the microstructure of the combustion synthesized TiB2/Cu composite. When Cu powders were smaller than 45µm, TiB2 particles were uniformly dispersed in Cu matrix. However, when Cu powders were larger than 150µｍ, monolithic Cu area without TiB2 dispersion was formed. The monolithic Cu area tended to be connected each other by increasing the amount of Cu powders. This resulted in the formation of 3-dimensionally continuous inter-penetrating TiB2/Cu microstructure.
Application of SPH for Modelling Heat Transfer and Residual Stress Generation in Arc Welding
Authors: Das Raj , Cleary Paul W.
Published: June 2010

An approach for three-dimensional modelling of thermo-mechanical responses in an arc welding process is developed using the Smoothed Particle Hydrodynamics (SPH) method. It is demonstrated for a simple arc welding configuration by solving the fully coupled three-dimensional elastoplastic and heat transfer analysis. The temperature distribution of the metal in the weld pool and the surrounding parent material are analysed using SPH, and the resulting residual thermal stresses are evaluated. This work establishes the capability of SPH as a tool for simulating the long-term thermo-mechanical responses, including heat transfer and residual stresses in a welded joint, and gaining insights into post-welding structural behaviour of joints during cooling stages.
A Study on B-Stage CNT / Epoxy Composite Films for Electronic Packaging Applications
Authors: Paik Kyoung Wook , Han Seung Hun
Published: June 2010

Carbon nanotubes (CNTs) have remarkable mechanical strength, electrical conductivity, and thermal conductivity in spite of low density. Recently, CNT / epoxy composite have been widely investigated in terms of fabrication process and material characterizations. However, there have been few previous studies on B-stage film type CNT / epoxy composites for electronic packaging applications. B-stage film type CNT / epoxy composite films were fabricated and their properties were characterized for electronic packaging applications. The most important issue on fabrication on B-stage epoxy based films were uniform dispersion of CNTs in an epoxy resin. In this study, using optimized dispersion process, CNT / epoxy films were coated on a releasing film and subsequently dried by the comma roll coating method. Curing behavior of B-stage films, mechanical properties and electrical properties of fully cured films were characterized as a function of CNT contents. According to experimental results, CNTs lowered the curing activation energy of epoxy resin and increased electrical conductivity of epoxy resin.
Superconductive Property and Microstructure of MgB2 Particle-Dispersed Aluminum Based Composite Materials
Authors: Mizutani Manabu , Matsuda Kenji , Makino Kazuya , Nishimura Katsuhiko , Kawabata Tokimasa , Hishinuma Yoshimitsu , Aoyama Shigeki , Ikeno Susumu
Published: June 2010

Superconducting wires have been applied for the fabrication of superconducting magnets in nuclear magneto-resonance (NMR), Magneto-resonance imaging (MRI) and so on. MgB2 has the highest critical temperature of superconducting transition (TC39K) among intermetallic compound superconductive materials. This means that MgB2 Superconductive wire doesn’t need expensive liquid He for cooling. We used the original method of the three-dimensional penetration casting (3DPC) in this laboratory to fabricate the MgB2/Al composite. Our 3DPC method for fabricating composite materials can disperse particles in the matrix homogenously without any aggregation and control volume fractions of composites within the range of 4 – 40%, even when particle size is less than 1 m. Thus, these composite materials can be processed by machining, extrusion and rolling. In the composite material we made, MgB2 particles dispersed to the Al matrix uniformly. The TC was determined by electrical resistivity and magnetization to be about 37 – 39K. We succeeded in extruding MgB2/Al composite billet to 1mm wire. Microstructures of these samples have been confirmed by SEM method. MgB2/Al composite billet and extruded wire were showed there no cracks inside the materials.
Hydrogen Storage in Nitrides by the Use of Ammonia as a Hydrogen Carrier
Authors: Imamura Hayao , Shimomura Naotaka , Watanabe Keisuke , Tanaka Kenichi , Nakamura Fumiya , Sakata Yoshihisa
Published: June 2010

Hydrogen storage by calcium nitride or magnesium nitride has been undertaken by the use of ammonia, in which the possibility of ammonia as a vector for hydrogen carriers has been studied. When the calcium imide ornitride obtained by thermal decomposition of calcium amide dispersed on active carbon (AC) was brought into contact with ammonia gas (300 Torr) at room temperature, NH3 uptake readily occurred. When the sample after NH3 uptake was heated, the absorbed ammonia was released in the form of hydrogen and nitrogen. The ammonia is possibly absorbed in the form of the decomposed state in the imide ornitride. This type of hydrogen storage has been extensively studied and characterized.For magnesium nitride, ammonia was absorbed and desorbed without the decomposition.
Hydrogen Permeation of Pd-Free V-Based Metallic Membranes for Hydrogen Separation and Purification
Authors: Kim Cheol Young , Chin Hong Seok , Yoo Gu , Park Kyoung Won , Fleury Eric
Published: June 2010

With the aim of replacing Pd coating layer currently used for the dissociation and recombination of hydrogen molecules, the performance of Nb and Ta thin layers as catalystforhydrogen permeationwas evaluated at 673 K.Although not as efficient as Pd, Nb and Ta coating layers can nevertheless provide a reasonable H2 dissociation and recombination rates. Thereduced values of hydrogen permeabilityin comparison to that of Pd were explained by the reduced catalytic properties of Nb and Ta and the formation of hydrides on the surface.
Influence of Temperature on Self-Discharge and High-Rate Discharge Characteristics of La-Rich AB5-Based MH Alloy Electrode
Authors: Zhou Huai Ying , Wang Pei Pei , Wang Zhong Min , Zou Rui Ping , Ni Cheng Yuan
Published: June 2010

The influence of temperature on self-discharge and high-rate discharge characteristics of MmNi3.65(CoAlMn)1.35 alloy electrode has been investigated by way of simulated battery tests. Self-discharge behaviors of the MH electrode were measured using two methods: continuous mode self-discharge and step mode self-discharge. The results indicate that both reversible and irreversible capacity loss of MH electrode are mainly affected by temperature and storage time. When tested at 323K, the gross capacity loss after storage for 4 days is 30.88%, 15.02% at 273K and 20.09% at 303K, respectively. SEM analysis has shown that some needle corrosion products are formed on the surface of MH electrode, especially following storage at high temperature. The efficiency of high-rate discharge process is related closely to its discharge current density (DCD) adopted in tests, discharged capacities decreased with increasing DCD, and the electrode performed good high-rate discharge behavior at 303 K. Cyclic voltammetry (CV) analysis has indicated that near linear relationships between Ip and Scan rate (v) have been observed in the three temperature cases. The calculated values of hydrogen diffusion coefficient (D) within the electrode, are 1.479×10-8 cm2 / s at 273K, 2.437×10-8 cm2 / s at 303K, and 3.156×10-8 cm2 / s at 323K, respectively.
The Effects of Cryogenic Milling and Catalytic Additives on the Hydrogen Desorption Behaviour of Nanostructured MgH2
Authors: Seo Chan Yeol , Wu Xiao Dong , Suzuki Kiyonori
Published: June 2010

It is well known that catalytic additives and mechanical milling are effective in improving hydrogen desorption kinetics of MgH2. In this study, the effect of catalytic additives including BaCa1-xNdxO3-δ (BCN) on the desorption behavior of MgH2 was investigated. It was found that BCN can improve the desorption kinetics, but not as effective as other known additives such as Nb2O5. The effect of milling temperature was also studied. It was found that the cryogenic milling is not as effective as room temperature milling primarily due to the inhomogeneous particle size distribution.
Effect of Flow Fields and Scan Rates on Performance of Micro-DMFC
Authors: Lu Yu Hao , Reddy Ramana G.
Published: June 2010

A micro-DMFC is a promising power source to substitute the lithium battery and used in the portable electronic devices. In this study, the effect of four types of flow fields of bipolar plates in a micro-direct methanol fuel cells (micro-DMFCs) on their performance were experimentally investigated. MEMS technology was applied in fabrication of micro-channel for the micro-DMFCs. The effect of the type of flow field design on the performance of micro-DMFCs was electrochemically evaluated for the four types of flow fields. The micro-DMFCs with double-channel serpentine presented the highest maximum power density and the micro-fuel cells with mixed multi-channel serpentine with narrow channels had the lowest maximum power density.
Rare Earth Element Aliovalent Doping Substitution and Electrochemical Performance of LiFe1-x NdxPO4
Authors: Zhao Min Shou , Zhang Li
Published: June 2010

LiFe1-xNdxPO4 /C cathode material has been synthesized by solid-state reaction. The structure and electrochemical performances of LiFe1-xNdxPO4 /C(x = 0 - 0.08) have been studied by XRD, FE-SEM, EIS and galvanostatic charge-discharge. The magnetization curve of LiFe1-xNdxPO4/C sample is measured by SQUID (Superconducting Quantum Interference Device) to examine if Fe3+ ion exists in LiFe1-xNdxPO4/C. The results show that a small amount of aliovalent Nd3+-dopant substitution on Fe+2 can effectively reduce the particle size of LiFePO4/C. The cell parameters of LiFe1-xNdxPO4 (x = 0.04 - 0.08) are calculated on Si internal standard, and LiFe1-xNdxPO4/C has the same olivine structure as LiFePO4, and delivers the highest discharge capacity of 165.2 mAh•g−1 at 0.2 C rate and the capacity retention rate is 92.8 % after 100 cycles. The charge transfer resistance decreases with adding glucose and Nd3+ ion. The measured theoretical capacity of 168.65 mAh∙g-1 is obtained. All the results imply that aliovalent doping substitution on Fe site in LiFePO4 is tolerant.
Joining of ODS Steels and Tungsten for Fusion Applications
Authors: Noh Sanghoon , Kasada Ryuta , Oono Naoko , Nagasaka Takuya , Kimura Akihiko
Published: June 2010

Liquid phase diffusion bonding between ODS steel and pure W was carried out and its joint strength was investigated for fusion applications. A block of high-Cr ODS ferritic steel and a W plate were diffusion bonded at 1240 °C for 1h with/without an insert material under an uni-axial compression load and a high vacuum atmosphere. Cross sectional microstructures of joint region were observed by scanning electron microscope and the mechanical properties of the joint region were evaluated by hardness test and torsion tests. Microstructure analysis revealed that high Cr ODS ferritic steel block and W plate with insert material was successfully diffusion bonded with free of voids. Shear strength of liquid phase diffusion bonded ODS steel and W was higher than that of directly solid state diffusion bonded ODS steel and W. This was attributed to residual strain which is resulted from the difference of thermal conductivity between the ODS steel and W.
Effect of Heat Treatment on Microstructure and Mechanical Properties of Low-Carbon TRIP Steel Tube
Authors: Zhang Zi Cheng , Zhu Fu Xian , Di Hong Shuang , Li Yan Mei , Manabe Kenichi
Published: June 2010

In this study, the effects of isothermal bainite treatment (IBT) holding time on the microstructure of transformation induced plasticity (TRIP) seamless steel tube were studied via optical microscopy, TEM and XRD. Its mechanical properties and hydroformability were evaluated by tensile test and flaring test, respectively. The results revealed that the volume fraction of retained austenite (RA) increased at first then decreased with IBT holding time for a particular set of intercritical annealing (IA) temperature, IA holding time and IBT temperature. It was also demonstrated that high tensile strength of 618MPa, total elongation of 35.5%, n-value of 0.23 and better hydroformability could be successfully produced in this TRIP steel tube at IA temperature of 800°C, holding for 10 min, and IBT of 410°C for 4 min holding time.
Visualization of Diffusive Hydrogen
Authors: Watakabe Takahito , Itoh Goroh , Hatano Yuji
Published: June 2010

In recent years, the use of hydrogen as a clean energy has been paid attention to in terms of the prevention of global warming. Tanks composed solely of steel and cylinders consisting of aluminum liner reinforced with C-FRP in the surrounding are used to store high-pressure hydrogen gas in hydrogen stations and in fuel cell vehicles, respectively. On the other hand, hydrogen embrittlement has been known to occur in some metallic materials under several certain conditions. Also, it has been generally known that the environmental hydrogen that invades the material during services plays major role in hydrogen embrittlement. For this reason, investigations on the behavior of environmental hydrogen in metallic materials are needed. In this study, the behavior of environmental hydrogen in pure aluminum, 6061 aluminum alloy and 7075 aluminum alloy has been investigated by means of tritium autoradiography.
Evaluation of Irradiation Hardening of Fe-Ion Irradiated F82H by Nano-Indentation Techniques
Authors: Takayama Yoshiyuki , Kasada Ryuta , Yabuuchi Kiyohiro , Kimura Akihiko , Hamaguchi Dai , Ando Masami , Tanigawa Hiroyasu
Published: June 2010

The effects of small amount (1 or 2 wt.%) of Ni additionson the irradiation hardening of the reduced-activation ferritic/martensitic steel, F82H, used as fusion reactor blanket structural materials were investigated by means of Fe-ion irradiation experimental test method and nano-indentation technique. The ion-irradiation hardening of Ni-added F82H is larger than that of the steel without Ni addition. The methodology to derive the irradiation hardening of ion-irradiated F82H steel was proposed from the results of hardness depth profile.
Microstructural Evaluation of Dy-Ni-Al Grain-Boundary-Diffusion (GBD) Treatment on Sintered Nd-Fe-B Magnet
Authors: Oono Naoko , Sagawa Masato , Kasada Ryuta , Matsui Hideki , Kimura Akihiko
Published: June 2010

A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the sintered Nd-Fe-B magnet plate as thick as 5mm to 1760 kA/m (22 kOe) without reducing the remanence. The results of wavelength dispersive X-ray spectroscopy (WDS) indicated that this industrially epoch-making treatment spread Dy, which is a coercivity enhancing element, from the surface to the centre of the magnet through Nd-rich phase. Microstructural observations suggested that Ni and Al, which are the melting point depressants of Nd and Dy, enabled the high diffusivity of Dy.
Chemical Property of Ground Calcium Carbonate as Carbon Dioxide Absorbent
Authors: Yokoyama Seiji , Muhd Nor Nik Hisyamudin , Hirano Shunsuke
Published: June 2010

Commercial sedimentation CaCO3 was ground by a vibration rod mill to investigate the physicochemical properties of mechanically activated CaCO3.When the CaCO3of the calcite structure was ground, the intensities of the crystal facesof calcite was decreased by distortions and so on, and the aragonite appeared as the grinding proceeded. The formed aragonite was transformed to the calcite when the sample was heated at 773K for3.6 ks. The dissociation pressure of CO2 of the ground CaCO3was larger than that of the non-ground CaCO3.The enthalpy; entropy and specific heat of change of the dissociation reaction were obtained. At high temperature, the emission rate of the ground CaCO3 was slightly larger than that of the non-ground CaCO3. At room temerature, the CaCO3 adsorbs CO2, and it desorbs the adsorbed CO2. The amount of adsorbed CO2 on the ground CaCO3 was larger than that of the non-ground CaCO3.
Effects of Processing Parameters on Microstructure Development in X70 Pipeline Steel
Authors: Al Shahrani A. , Schambron Thomas , Dehghan-Manshadi Ali , Williams James G. , Pereloma Elena V.
Published: June 2010

Achieving fine and uniform grains is the most effective way to enhance strength and toughness, which are required properties for pipeline steels. Steels microalloyed with Nb can exhibit a mixed grain structure, which can deteriorate low temperature toughness. In this work the effects of the thermomechanical processing parameters on the prior austenite grain structure before ferrite transformation have been investigated.
Influence of Phosphorous and Boron on the Recrystallization, Grain Growth and Mechanical Properties of 3% Si Steel
Authors: Lee Se Il , De Cooman Bruno C.
Published: June 2010

A new approach to obtain high strength of non-oriented electrical steel by addition of phosphorus is proposed. The method includes B-additions which suppress grain boundary P segregation, strengthen the grain boundary cohesion and enhance the P solid solution hardening. Two 3% Si steels, a B-free 0.1%P steel and a 20 ppm B-added 0.1%P steel were analyzed. The microstructures were studied by EBSD. The B-addition resulted in a pronounced rotated cube component, {100}<011>, after a hot-band annealing treatment. A -fiber texture was developed in the B-free steel. The B-addition caused a retardation of the recrystallization, allowing for the growth of grains with a lower stored energy, such as rotated cube oriented grains. The steels were further cold rolled and recrystallization annealed to observe a similar effect after large cold reductions. The present contribution focuses on the potential of this concept to obtain high strength 3% Si steels with low core losses.
Influence of Initial Microstructure on Mechanical Properties of Cu Bearing Extra Low Carbon Steel Sheets
Authors: Min Sim Kun , Kim Sung Il , Kim Jong Sang , Hong Moon Hi
Published: June 2010

This paper examines the effect of initial microstructure after hot rolling on the final microstructure and mechanical properties for Cu bearing Extra Low Carbon(ELC) Steel Sheets. For this purpose, two ELC steels having different initial microstructures due to different onset time of cooling after pilot hot rolling (0.4 and 1.2 second) were selected. Mechanical properties and microstructures were analyzed as well using uni-axial tensile test, electron back-scattered diffraction (EBSD) technique following pilot rolling and continuous annealing. It has been found that the reduction of onset time of cooling gives rise to the grain refinement in hot rolled sheets. The average grain sizes of hot rolled sheetss at the onset time of 0.4 and 1.2 second are 16.7μm and 20.8 μm, respectively. In addition, the planar anisotropy of the Cu bearing ELC steel sheets has improved with reducing onset time of cooling after hot rolling. However, other mechanical properties such as strength and elongation of annealed steel are similar to both cooling condition.
Hot Deformation Behavior of V-Microalloyed Steel
Authors: Ren An Chao , Ji Yu , Zhou Gui Feng , Yuan Ze Xi , Han Bin , Li Yi , Yang Jing
Published: June 2010

The dilatation curves of continuous cooling transformation at different cooling rates were determined for U75V rail steel by THERMECMASTOR-Z thermal simulator, and continuous cooling transformation curve was obtained. The influence of cooling rate on microstructure and hardness was studied. The softening behavior after isothermal deformation in the austenite region 850-1000°C but before the second pass was also studied by double-pass compression tests. The results show that the product of austenite decomposition was pearlite when the cooling rate was lower than 10°C. Troostite and martensite were gained at the cooling rate of 10°C•s-1. Only martensite was obtained when the cooling rate was in the range of 10-50°C•s-1. The hardness of the steel increased with the increase of cooling rate. Under the condition of 30% deformation and 3s-1 deformation rate, the relaxation time for completing recrystallization was shorter than 100s when the deformation temperature was higher than 1000°C. When the deformation temperature was lower than 880°C, full recrystallization was difficult to achieve even if the relaxation time was extended.
Influence of Strain Path Changes on Microstructure Inhomogeneity and Mechanical Behavior of Wire Drawing Products
Authors: Muszka K. , Wielgus M. , Majta Janusz , Doniec K. , Stefanska-Kadziela Monika
Published: June 2010

Cold drawn low carbon steel wires are widely used in several engineering applications where a proper combination of strength and ductility is of the paramount importance. In the present paper, the multi-pass angular accumulative drawing (AAD) is proposed as a new forming process where the high strain accumulation is used as a way to achieve much higher microstructure refinement level compared to the conventional wire drawing process. This process is characterized by a complex strain path history, being an effect of wire diameter reduction, bending, tension and torsion, what directly affects the microstructure changes in the final product. This process also evolves high inhomogeneity of microstructure, that if properly controlled, can lead to further properties improvement - what can be especially beneficial for alloys that are not characterized by complex compositions. In the present paper, special emphasis is given on the inhomogeneity of both deformation and microstructure and resulted mechanical properties. After drawing and annealing (at 500oC) mechanical properties measurements and microstructure analysis on the longitudinal sections of the wires were performed to assess the differences existing with respect to the conventional wire drawing process.
Evaluation of Press Formability Using Servo Die Cushion in Deep Drawing
Authors: Watanabe Akihiro , Kotani Yuji , Watari Hisaki , Shimizu Takehiro
Published: June 2010

Manufacturing process using servo press machines have been highlighted in car manufacturers and other industries in Japan. It is necessary to establish an appropriate press working conditions for manufacturing highly accurate products with great extra value. Our aim is to investigate into effects of variable BHF (blank holding force) on press formability, comparing to using a conventional press machine. In this study, FEM analyses of deep drawing process using a variable BHF system has been conducted to demonstrate the effectiveness of a servo die cushion on formability. According to experimental results obtained with a servo die cushion, it is found that maximum load subjected to dies was reduced by 11.8 %, when using a servo press with a servo die cushion comparing to a conventional press.
Influence of Thermal History on Microstructure and Mechanical Properties of Steels for Hot Stamping
Authors: Senuma Takehide , Takemoto Yoshito
Published: June 2010

Hot stamping is an attractive method to produce extra high strength automotive components. In the conventional hot stamping, the furnace heating is employed and the heating rate is quite low. To improve the productivity of the hot stamping technology, the reduction of time for the heating process is required. In this study, the influence of the heating rate in a range up to 200°C/s, heating temperatures between 650°C and 950°C and cooling condition on microstructure and mechanical properties of 0.22% C -3%Mn steel has been investigated. The steel is a promising material for the highly productive new hot stamping technology because this steel transformed into martensite from austenite even at cooling in free air. The specimens heat-treated at a high heating rate and for short holding time at the heating temperature just above Ac3 show significantly fine martensite microstructure and a good strength-toughness balance. In this paper, the α→ γ transformation behavior and the γ→ α transformation behavior after inter-critical annealing are discussed to explain the evolution of the microstructures and mechanical properties.
Effect of Carbon on Frictional Wear Behaviours of High Vanadium High Speed Steel under Dry Sliding Condition
Authors: Xu Liu Jie , Wei Shi Zhong , Ji Ying Ping , Zhang Guo Shang , Li Ji Wen , Long Rui
Published: June 2010

The high vanadium high-speed steel (HVHSS) with about 9wt% vanadium and different carbon contents were prepared using casting process. The effects of carbon on wear properties of HVHSS were studied using pin-on-ring tester, and the failure behaviors were investigated via SEM. Results show the optimal wear resistance is obtained when HVHSS possesses moderate carbon content (2.58wt.%). The cause is that the matrix microstructure of moderate carbon HVHSS is mainly low-carbon lath martensite with good toughness and high hardness, and it can effectively resist micro-cutting and figure wear at the same time, so the role of high-hardness vanadium carbides (VC) can be played enough because of the strong support of matrix. If carbon content is too low, the wear failure of HVHSS is mainly caused by severe micro-cutting and adhesive wear on contact surface because the matrix microstructure of high speed steel is ferrite with very low hardness, which leads to poor wear resistance. While, the matrix microstructure is mainly composed of high carbon martensite with poor toughness when carbon content is too high, therefore, it possesses very poor resistance to cycle fatigue and thermal fatigue, resulting in decrease of wear resistance.
Effect of Microshot Peening on Surface Characteristics of Spring Steel
Authors: Harada Yasunori , Yoshida Koji
Published: June 2010

Shot peening is a surface treatment that improves the performance of engineering components. In conventional shot peening, the medium consists of small spheres, which are usually made of high-carbon cast steel; the diameter of the spheres is in the range from 0.3 to 1.2mm. More recently, however, a new type of microshot has been developed to enhance the peening effect. The diameter of the spheres in the new medium is in the range from 0.02 to 0.15mm. In the present study, the effect of microshot peening on the surface characteristics of spring steel was investigated. The injection method of the microshot was of the compressed air type. The microshots of 0.1mm diameter were high-carbon cast steel and cemented carbide, and the workpiece used was the commercially spring steel JIS-SUP10. The surface roughness, hardness and compressive residual stress of the peened workpieces were measured. The surface layer of the workpieces was sufficiently deformed by microshot peening. A high hardness or residual stress was observed near the surface. The use of hard microshots such as cemented carbide was found to cause a significantly enhanced peening effect for spring steel.
Mold Thermocouple Locations and their Impact on Prevention of Caster Breakouts
Authors: Sohn Il , Sinha Asish
Published: June 2010

With advances in mold instrumentation, high performance mold fluxes, better reliability maintenance procedures, and improved operating practices, there has been a significant decline in the number of unplanned caster breakouts experienced at various production facilities. The typical breakouts of stickers and flux entrapments that were frequently observed in the past is often detected using embedded thermocouples in the mold and automatic slowdowns are initiated which inhibit excessive tearing of the partially solidified shell and prevent subsequent breakouts. However, in-mold events still occur resulting in caster downtime. Many of these occasional events have been linked to bleeders along the corners of the slabs, slab joint defects during tundish changes, and longitudinal face cracking. Considering the potential costs associated with unplanned caster breakouts, improvements have been made in the existing breakout prevention system. Major modifications of this existing breakout prevention system included, in particular, the addition of bleeder thermocouples or edge thermocouples which made possible the detection of shell containment loss near the corners of the slab. These bleeder thermocouples can also be utilized in detecting bad tundish joints related to excessive cooling and corner contraction that lead to tundish change joint defect type breakouts. In addition, changes in the location of the existing embedded thermocouples to a staggered-design extended the detection range of the breakout prevention system without increasing the total number of thermocouples.
Mo Effect on the Microstructure in Co-Al-W-Based Superalloys
Authors: Xue Fei , Li Zhi Qiang , Feng Qiang
Published: June 2010

The as-cast and heat-treated microstructure has been investigated in Co-Al-W-based superalloys with additions of 2 and 4 at.% Mo. The results revealed that Mo promoted the formation of (μ+γ) eutectic structure in the as-cast alloys and μ-phase precipitation after solution treatment. In addition, after aging treatment at 900oC, an extensive network of DO19 precipitates was observed, besides the γ+γ′ primary phases and the μ phase inherited from the as-cast and solution-treated conditions. Meanwhile, a solid-state transformation from the μ phase to the DO19 phase occurred; and long-term aging enhanced this transformation. In addition, high levels of Mo promoted the DO19-phase precipitation.
High Temperature Strength of Ir/Ir2Y Two Phase Alloys in the Ir-Pt-Y System
Authors: Sekido Nobuaki , Yamabe-Mitarai Yoko
Published: June 2010

Possibilities of heat resistant alloys based on a C15 Laves phase and an FCC phase have been examined in the Ir-Pt-Y ternary system. Although the Ir solid solution phase (A1) and the Ir2Y phase (C15) are not in equilibrium in the Ir-Y binary system, this equilibrium is attained by small Pt additions to the binary system. High temperature compressive strength of an A1/C15 monovariant eutectic alloy was found to be much lower than that of Ir-15Nb, an Ir based γ/γ' alloy. Low strength of the present alloys is attributed to the absence of effective strengthening mechanisms that operate in the A1 phase; for Y is hardly dissolved within the A1 phase, by which solution hardening and precipitation hardening are not available.
Phase Transition and Ordering Temperatures of TiAl-Mo Alloys Investigated by In Situ Diffraction Experiments
Authors: Schmoelzer Thomas , Mayer Svea , Haupt Frank , Zickler Gerald A. , Sailer Christian , Lottermoser Lars , Güther Volker , Liss Klaus Dieter , Clemens Helmut
Published: June 2010

Intermetallic TiAl alloys with a significant volume fraction of the body-centered cubic β-phase at elevated temperatures have proven to exhibit good processing characteristics during hot-working. Being a strong β stabilizer, Mo has gained importance as an alloying element for so-called β/γ-TiAl alloys. Unfortunately, the effect of Mo on the appearing phases and their temperature dependence is not well known. In this work, two sections of the Ti-Al-Mo ternary phase diagram derived from experimental data are shown. These diagrams are compared with the results of in-situ high-temperature diffraction experiments using high-energy synchrotron radiation.
The Effect of Grain Size on Cutting Force in End Milling of Inconel 718C
Authors: Zhao Zhi Long , Ai Chang Hui , Liu Lin
Published: June 2010

Inconel 718C is a nickel-base alloy that is difficult to machine. This paper presents a study of the influence of grain size in as-cast workpieces on cutting forces of Inconel 718C. The end milling tests were performed to understand the effect of various grain structures on machinability of nickel-base superalloy under wet condition using carbide insert. The collected data of cutting forces were analyzed using polynomial regression methods. The results show that grain refining of Inconel 718C can effectively decrease cutting force and improve the machinability of nickel-base superalloy.
The Effect of Heat Treatments on Microstructure and Creep Properties of Powder Metallurgy Beta Gamma Titanium Aluminide Alloys
Authors: Sawatzky Trevor , Seo Dongyi , Saari H. , Laurin D. , Kim Dae Jin , Kim Young Won
Published: June 2010

The microstructure and creep properties of two powder metallurgy (PM) ‘beta gamma’ titanium aluminide alloys are presented. Alloy powders with nominal compositions of TiAl-4Nb-3Mn (G1) and TiAl-2Nb-2Mo (G2) were produced by gas atomization and consolidated by a two-step hot isostatic pressing (HIP) process (1250 °C/200 MPa/1 hour + 1100 °C/200 MPa/3 hours + slow cooling to room temperature). After HIP, the materials were given a step cooled heat treatment (SCHT) of 40 min at 1400 °C, furnace cooling to 1280 °C, and air cooling to room temperature. Selected specimens were aged at 900 °C for 6 or 24 hours. The SCHT yielded similar fully lamellar microstructures for both alloys, with a lamellar spacing of 0.04 m, but with different grain sizes averaging 80 m (G1) and 40 m (G2). The aging treatments generated  precipitates along lamellar colony boundaries in both alloys, but along lamellar interfaces only in alloy G2. Constant load tensile creep tests were performed at 760 °C and 276 MPa. Alloy G2 exhibited superior creep performance compared to alloy G1, due to the quantity and size of  precipitate particles at the lamellar interfaces.
The Effect of Inclusions on Mechanical Behaviour in Ultra-High Strength Alloy Steels
Authors: Xie Xi Shan , Zeng Yan Ping
Published: June 2010

Inclusions are un-avoidable even in super-clean engineering alloy steels because of the necessary melting process. These inclusions (such as TiN, AlN etc) are considered as harmful phases especially for ultra-high strength alloy steels. The unique experiments (in-situ tension and in-situ fatigue tests) have been conducted in a loading chamber of scanning electron microscope. TiN often characterizes with large blocky cubic morphology. Cracks easily initiate at the sharp corners of TiN cubic particles or sometimes directly initiate in TiN particles because of its brittleness. These cracks propagate to the matrix and to introduce early failure. AlN small particles (in several microns) often distribute as inclusion chains in steels. At tensile and fatigue tests cracks very often initiate at the inclusion chains among AlN small particles and line up to develop voids, which rapidly propagate to the matrix till early failure. These important results reveal the harmful effect of inclusions in micro-scale and can be connected with tensile and fatigue loading processes for understanding the early failure mechanisms.
Creep Crack Growth Rates on the Base and Welded Metals of Modified 9Cr-1Mo Steel
Authors: Kim Woo Gon , Park Jae Young , Yin Song Nan , Kim Yong Wan , Kim Seon Jin
Published: June 2010

This study aimed to assess creep crack growth rates on the base and welded metals of modified 9Cr-1Mo steel. For this purpose, welded specimens were prepared by the Shielded Metal Arc Weld method. To obtain mechanical properties concerning the base and welded metals, a series of creep and tensile tests were conducted at 600 °C, and creep crack growth tests were also performed under different applied loads using 1/2" compact tension specimens at 600 °C. Their creep crack growth rates were calculated using the empirical equation of the da/dt vs. C* parameter and compared. It appeared that, for a given value of C*, the rate of creep crack propagation was about 2.0 times faster in the welded metal than the base metal. This reason was that the welded metal was faster in the creep strain rate than the base metal.
Evaluation of Creep-Fatigue Crack Growth for Grade 91 Steel Wide Plate
Authors: Lee Hyeong Yeon , Kim Jong Bum , Lee Jae Han
Published: June 2010

An assessment of a creep-fatigue crack growth for Mod. 9Cr-1Mo steel wide plates have been carried out based on an extended French high temperature design code, RCC-MR A16 guide. The defect assessment guide of the A16 provides assessment procedures on creep-fatigue crack growth for an austenitic stainless steel, but no guidelines are available yet for a Mod. 9Cr-1Mo steel. In this study, assessments of a creep-fatigue crack growth at defects of Grade 91 steel wide plates have been carried out based on the extended A16 method for austenitic stainless steel.
Formation of Protective Intermediate Phase in Ta Addition TiAl during High Temperature Oxidation
Authors: Hashimoto Keizo , Seita Kyoichi
Published: June 2010

The mechanical properties and the oxidation resistance of -TiAl at elevated temperatures have to be improved to be used in the severe environmental conditions. It has become clear that the addition of more than 4at.%Ta in TiAl demonstrates a superior oxidation to the other TiAl-X compounds, according to the weight gain results of cyclic oxidation experiments at 1173 and 1273K. Oxidation behaviors are strongly influenced by the Ta concentration in TiAl. XRD, SEM-EDS, and TEM-EDS observations have been carried out to determine the microstructures and the surface compositions of multi-layered oxide scales. It was revealed that a protective intermediate phase simultaneously formed between the substrate γ-TiAl and the oxide scale layer. The Ti53Al32Ta15 ternary compound exists as an equilibrium phase at 1373K, according to the published Ti-Al-Ta ternary phase diagram. This ternary compound can work as a barrier to some extent. It contributes to decelerating the diffusion of Ti and Al atoms and to decreasing the oxidation rate. The formation mechanism of the intermediate phase has been discussed in conjunction with diffusion in TiAl.
High Temperature Alloys from Nb-Cr-Si System with Minor Additions
Authors: Portillio Benedict , Alvarez David , Vazquez Alma , Varma Shailendra K.
Published: June 2010

Several Nb based alloys (Nb-20Mo-15Si-25Cr, Nb-20Mo-15Si-25Cr-5B, Nb-20Si-20Cr-5Al, and Nb-20Cr-20Si-5Hf) have been prepared to evaluate the oxidation resistance from 700 to 1400°C in air. The phase identification was determined by calculating the isothermal sections in this temperature range using PANDATTM software. The experiments involve static heating for 24 hours (short term oxidation, STO) or 7 cycles of 24 hour heating (long term oxidation, LTO). Weight gain per unit area as a function of either temperature (STO) or time (LTO) has been used to determine their oxidation resistance. However, SEM, EDS on SEM, x-ray mapping, and XRD have been used to evaluate the oxide scale characterization and the influence of various microconstituent effects have been determined. It appears that B addition may be beneficial while Al is advantageous in comparison to Hf addition. The problem of pesting, typically, in a range of temperature from 900 to 1100°C needs to be controlled through minor additions since the alloys exhibit fairly good resistance at lower and higher temperatures up to 1400°C.
Development of the Microstructure and Texture of RE Containing Magnesium Alloys during Hot Rolling
Authors: Kainer Karl Ulrich , Wendt Joachim , Hantzsche Kerstin , Bohlen Jan , Yi Sang Bong , Letzig Dietmar
Published: June 2010

Commercial magnesium alloys such as AZ31 exhibit strong crystallographic textures during massive deformation such as rolling. A randomisation of the texture, however, was found in alloys with rare earth (RE) elements in solid solution. This paper describes the development of microstructure and texture during rolling of the Al-free RE-containing wrought magnesium alloy ZEK100 during hot rolling. This alloy develops a strong texture with a pronounced component towards the transverse direction (TD) of the sheets. This TD component forms already after the first rolling pass, persists through all following passes and is further enhanced by subsequent heat treatment. These results are contrasted with results from a study on texture development of binary RE containing Mg-alloys, which show that the presence of RE elements alone is not responsible for the tilt of basal planes towards the TD. There is, however, a threshold concentration at which the texture begins to weaken.
Microstructure and Joint Strength of Similar- and Dissimilar Lap Joints Fabricated by Several Advanced Solid-State Welding Methods
Authors: Kumai Shinji , Watanabe Mitsuhiro , Feng Keyan
Published: June 2010

Both similar- and dissimilar metal joints, which are difficult to be welded by using ordinary fusion welding methods, were successfully obtained by using several advanced high-speed solid-state joining methods. (1) Al/Al, Cu/Cu, Al/Fe(Steel), Al/Cu, Al/Ni, Cu/Ni and Al/Bulk metallic glass lap joints were magnetic pulse welded by means of mutual high-speed oblique collision of metal sheets at a high speed of about 500m/s. (2) 2xxx aluminum alloy pins were stud-welded to 5xxx alloy aluminum sheets and several kinds of plated steel sheets at a high speed by using a specially designed discharge circuit. The welding was achieved within a few milliseconds without producing any weld marks on the back surface of the plate. (3) 6022 aluminum alloy sheets were friction stir spot welded to steel sheets and various kinds of galvanized and aluminum-plated steel sheets. The welding was achieved within a few seconds. For those joints, joint strength and characteristic joint interface morphology were investigated.
Building Capability through Benchmarking and Technology Transfer
Authors: Hodge R. Mark , Palanisamy Suresh , Dargusch Matthew S.
Published: June 2010

Production, sustainment and repair technologies for light alloy components in the defence applications account for a significant proportion of Defence Materials Technology Centre (DMTC) activities. Key challenges in this regard include the affordable manufacture and repair & sustainment of Titanium components for new and legacy platforms. The DMTC research program portfolio incorporates collaborative technology development activities between industry and the research sector within a framework of a partnership model that includes input from the Defence customer on likely procurement opportunities for industry, and longer term strategic requirements of Defence. The technological focus is particularly on the benchmarking of strategies, technologies and manufacturing techniques associated with the manufacture of aerospace components via high speed machining. Developing affordable, cost-effective and best of breed machining processes and practices among a broad range of Australian manufacturing organisations is a key goal of the DMTC. This paper describes an initiative of the DMTC focused on developing and optimising engineering capability in metals manufacturing for aerospace applications. Data generated from a range of participating sources conducting machining trials of identical titanium and stainless steel components is compared and contrasted in the context of best practice development.
Multimodal Microstructure Evolution in Wrought Mg-Zn-Y Alloys with High Strength and Increased Ductility
Authors: Yamasaki Michiaki , Hashimoto Kenji , Hagihara Koji , Kawamura Yoshihito
Published: June 2010

High strength and ductile Mg96Zn2Y2 (at%) alloys with multi-modal microstructure are developed. Microstructure of the extruded Mg96Zn2Y2 alloy consists of three regions; the dynamically recrystallized -Mg fine-grains region, the hot-worked -Mg coarse-grains region elongated along extrusion direction, and the long-period stacking ordered (LPSO) phase region with kink deformation bands. Bimodal microstructure evolution in -Mg matrix is influenced by the morphology of the LPSO phase in the as-cast state, therefore, the effect of secondary dendrite arm spacing in cast state on the microstructure evolution and mechanical properties of the extruded Mg-Zn-Y alloy is investigated. An increase in the dynamically recrystallized grains improves ductility of the extruded alloys; the effective dispersion of the LPSO phase enhances strengthening of the alloy.