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Showing papers in "Materials Transactions in 2011"


Journal ArticleDOI
TL;DR: The main Aluminium applications as state-of-the-art in European cars are presented in this article and new studies and innovative multi-material concepts are discussed where Aluminium light-weight solutions are compared with that of other materials, like new steels, magnesium, plastics and composites.
Abstract: The main Aluminium applications as state-of-the-art in European cars are presented. The main established Aluminium alloys and their application in automotive parts are presented together with recent developments. Also new studies and innovative multi-material concepts are discussed where Aluminium light-weight solutions are compared with that of other materials, like new steels, magnesium, plastics and composites. In the “SLC” (Super-Light-Car) project these new concepts were tested in a multi-material body-in-white prototype for a VW Golf V car, reaching a 34% weight reduction within a cost increment of 7,8 €/kg saved, with suitable technologies for high volume assembly cycles. In the final SLC concept Aluminium is the material of choice, proving its leading role in innovative light-weighting of cars. Aluminium achieves weight savings of parts up to 50% while maintaining safety and performance in a cost efficient way, competing efficiently with other light-weight materials.

380 citations


Journal ArticleDOI
TL;DR: In this article, the tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg 1.5Mn alloys.
Abstract: The tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg-1.5Zn0.1Ca, Mg-3Zn, Mg-3Zn-0.1Ca, Mg-3Al, Mg-3Al-0.1Ca and Mg-1Al-1Zn-0.1Ca-0.5Mn alloys. In the Mg-Zn alloys, the 0.2% proof stress at 90 � , which was the angle between the tensile direction and the RD, was decreased by addition of Ca, while the 0.2% proof stress at 0 � was increased by addition of Ca. Also, an increase in elongation to failure by addition of Ca at 90 � was larger than that at 0 � . However, such variations in tensile properties by addition of Ca were not found in the Mg-Al alloy. The stretch formability for the Mg-Zn alloys was significantly enhanced by addition of Ca, while the stretch formability of the Mg-Al alloy was not enhanced by addition of Ca. These results by the mechanical testing are ascribed to the variations in basal texture by addition of Ca. [doi:10.2320/matertrans.M2011048]

164 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of temperature on irradiation hardening and microstructure development in irradiated tungsten-rhenium (W-Re) alloys was investigated.
Abstract: The aim of this work is to investigate the influence of neutron irradiation condition, especially temperature, on irradiation hardening and microstructure development in irradiated tungsten-rhenium (W-Re) alloys. Neutron irradiations were carried out in JOYO at the range of 400 to 750 � C, up to 1.54 dpa. Micro Vickers hardness tests and micro structural observations using a TEM were performed. Irradiation hardening of WRe alloys irradiated at 538 � C were clearly larger than those irradiated at other temperatures. Fine voids and fine needle- or plate-like precipitates were observed in pure W and W-Re alloys irradiated at 538 � C, respectively, with high number density. The fine complex microstructure seems to be the cause of the characteristic irradiation hardening. [doi:10.2320/matertrans.MBW201025]

113 citations


Journal ArticleDOI
TL;DR: In this paper, a Rietveld-type analysis code, RITS, was developed to obtain the information on preferred orientation and crystallite size at the same time from the Bragg-edge transmission spectrum.
Abstract: Bragg-edge transmission imaging using a pulsed neutron source is expected to be a new method to investigate the crystallographic and metallographic structure of a material. This method has attracted the attention in the research field of material characterization for materials development and industrial applications because it non-destructively provides the images on the texture and the microstructure inside a material such as a thick steel bulk over the wide area of the material. For deducing such information from the Bragg-edge transmission spectrum, a data analysis code like a Rietveld analysis code for powder diffractometry is indispensable. So far, only the information on the crystallographic anisotropy has been deduced. However, this information is incomplete since both the preferred orientation and the crystallite size affect the Bragg-edge transmission spectrum. Therefore, we have developed a Rietveld-type analysis code, RITS, that allows us to obtain the information on preferred orientation and crystallite size at the same time. To examine the feasibility and the usefulness of the RITS code, we have analyzed the Bragg-edge transmission spectra of rolled and welded � -iron plates, and we have successfully obtained the preferred orientation data and the crystallite size data over the wide area of the bulk specimens. [doi:10.2320/matertrans.M2010328]

109 citations


Journal ArticleDOI
TL;DR: The crystal structures and microstructures of precipitates formed in an Mg-0.5 at%Nd alloy aged at certain temperatures ranging between 170 C and 250 C are studied in detail by high-angle annular detector dark-field scanning transmission electron microscopy.
Abstract: The crystal structures and microstructures of precipitates formed in an Mg-0.5 at%Nd alloy aged at certain temperatures ranging between 170 C and 250 C are studied in detail by high-angle annular detector dark-field scanning transmission electron microscopy. The precipitation sequence can be presented as Mg-solution! GP-zone! 0 (orthorhombic) ! 1 (fcc). At the early stage of aging (170 C for 2 h), fine precipitates of planar GP-zones appear in parallel to (100)m planes, with a thickness of sub-nm and a length of 5–15 nm (the subscript letter of m denotes matrix). With an advance of aging, the GP-zones increasingly grow larger and combine with the neighbours, thus making themselves further prolonged along the directions addressed above. When reaching at the top-stage of aging (170 C for 100 h), the alloy additionally allows the 0-phase to coexist, taking the form of lens-shape with a thickness of 2–5 nm and a diameter of 5–15 nm. The 0-phase has an orthorhombic structure (Mg7Nd) with a 1⁄4 0:64 nm, b 1⁄4 1:1 nm, and c 1⁄4 0:52 nm, which is coherently connected to the matrix. At the stage of over-aging, both the GP-zones and the 0-phase disappear and instead coarse precipitates of the stable 1-phase (Mg3Nd; fcc) are formed with particular crystallographic relations of 1⁄2001 m == 1⁄2110 p and 1⁄2110 m == 1⁄2112 p (the subscript letter of p denotes precipitate). [doi:10.2320/matertrans.M2011163]

100 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of a change in the stacking sequence of the close-packed plane in a Mg12ZnY long-period stacking ordered (LPSO) phase on its mechanical properties was investigated.
Abstract: We investigated the influence of a change in the stacking sequence of the close-packed plane in a Mg12ZnY long-period stacking ordered (LPSO) phase on its mechanical properties. A 14H-typed LPSO-phase crystal was fabricated by annealing a directionally solidified (DS) crystal with a 18R-typed LPSO-structure at 525°C for 3 days, and the temperature dependence and orientation dependence of the yield stress were examined via compression tests. (0001)〈11\\bar20〉 basal slip was identified as a dominant deformation mode, and deformation kink bands were formed under compression in the case of suppression of basal slip motion. The deformation mechanism of the 14H-typed LPSO-phase is almost similar to that of the 18R-typed LPSO-phase, even though a slight difference was observed at temperatures above 300°C.

95 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed an Advanced Polymer-Metal Hybrid Structures (AMPHS) for the Solid State Joining Processes (SSPP) at the Max-Planck-St. 1, D-21502 Geesthacht.
Abstract: Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Solid State Joining Processes, Max-Planck-St. 1, D-21502 Geesthacht, Germany Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Advanced Polymer-Metal Hybrid Structures, Max-Planck-St. 1, D-21502 Geesthacht, Germany Federal University of Sao Carlos (UFSCar), Departamento de Engenharia de Materials (DEMa), Rodovia Washington Luiz km 235, 13565-905 São Carlos-SP, Brazil

78 citations


Journal ArticleDOI
TL;DR: In this paper, a thin plasma-sprayed aluminum interlayer was used to fabricate lower volume resistivity coating on cold spray, and the interlayer with larger contact area could retain on the substrate and able to facilitate the deformation of the next incoming cold spray particles to build a thick coating.
Abstract: Carbon fiber-reinforced plastic (CFRP) has a great potential application in aircraft fuselage due to its light weight, high specific stiffness and high specific strength. It is crucial to coat the CFRP surface with an electrically conductive material to avoid the damage from lightning strike. Cold spray process has been developed for metallic coating technique. In this study, aluminum coating was fabricated onto the CFRP substrate using interlayer was investigated. It was difficult to fabricate cold-sprayed aluminum coating directly on the CFRP substrate. Though smaller size aluminum particles could be deposited on the CFRP substrate, but the coating was peeled off when the thickness was around 30 mm. On the other hand, it was possible to deposit aluminum coating on the CFRP substrate by plasma spray process. Our proposed structure is using a thin plasma-sprayed aluminum interlayer on the CFRP substrate before doing the cold spray. The interlayer with larger contact area could retain on the substrate and able to facilitate the deformation of the next incoming cold-sprayed particles to build a thick coating. The volume resistivity of cold spray coating is lower than the plasma sprayed aluminum coating because of high process gas temperature in the latter case enhances the oxidation of sprayed particle. Therefore, lower process gas temperature should be used to fabricate lower volume resistivity coating on cold spray. [doi:10.2320/matertrans.T-M2011807]

73 citations


Journal ArticleDOI
TL;DR: In this paper, the weldability of duralumin and titanium alloys using friction stir welding was investigated, and the average tensile strength of the Ti/2024 FSW joints was 311 MPa.
Abstract: The friction stir welding (FSW) process is a solid-state joining process and the joining temperature is lower than that used in the fusion welding processes. Therefore, for dissimilar metal welding, FSW is considered to offer several advantages over fusion welding. The present work investigated the weldability of duralumin and titanium alloys using friction stir welding. The aluminum plates used in this work were 2024T3 and 7075-T651, and the titanium plates used were pure titanium and Ti-6Al-4V. The average tensile strength of the Ti/2024 FSW joints was 311 MPa, and the tensile strength of the Ti/2024 joint was higher than that of the Ti/7075 FSW joint when the joining conditions were the same. A mixed region of Ti alloy and Al alloy was observed at the joint interface, and the joints mainly fractured at this region, where there was an intermetallic compound layer. In this region, a TiAl3 intermetallic compound was detected by XRD. Therefore, it can be understood that this TiAl3 intermetallic compound affects the tensile strength of butt joints. [doi:10.2320/matertrans.L-MZ201102]

65 citations



Journal ArticleDOI
Ki-Sang Bang1, Ki-Sang Bang2, Kwan-gjin Lee2, Han-Sur Bang1, Hee-Sun Bang1 
TL;DR: In this article, a unique shaped tool with circular truncated cone of probe was used to perform friction stir welding (FSW) about AA6061-T6 and Ti-6Al-4V alloy sheets.
Abstract: Friction stir welding (FSW) was performed about AA6061-T6 and Ti-6Al-4V alloy sheets. A unique shaped tool with circular truncated cone of probe was used. Mechanical properties and interfacial microstructure were evaluated using tensile test, hardness test, optical microscopy (OM), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), respectively. Root area of probe in stir zone (SZ) reveals a mixture of finely recrystallized grains of Al and Ti particles pushed away from the base metal by strong stirring of probe. The joint interface of tip area of probe was relatively flat because stirring between aluminum and titanium alloy was not occurred due to the gap of the probe and titanium alloy front. It is considered that the insufficient stirring due to inclined side of the probe was contributed to the decrease of weld strength. After tensile test, fracture surface was analyzed by SEM. In the probe root area, dimples of Al were observed. In the probe tip area, the initial surface of titanium alloy plate was observed. However, in the middle area, similar amount of Ti and Al was detected. As result, it was confirmed that the fracture sequence was very complex and the fracture position was different according to the probe position. [doi:10.2320/matertrans.L-MZ201114]

Journal ArticleDOI
TL;DR: In this article, the weld metal in multi-pass Alloy 52-A508 dissimilar welds was examined and an approximately 2mm wide transition zone was observed that consisted of a martensitic layer (10 20 um) along the weld interface and the austenite phase region with varying degrees of dilution.
Abstract: In the nuclear power industry, dissimilar metal welding is widely used for joining low alloy steel to austenite stainless steel components with nickel-base filler metals. In this study, attention was paid to the weld metal in multi-pass Alloy 52-A508 dissimilar welds. An approximately 2mm wide transition zone was observed that consisted of a martensitic layer (10 20 um) along the weld interface and the austenite phase region with varying degrees of dilution. After post-weld heat treatment, the microstructures near the weld interface consisted of martensite, carbides and Type II boundaries. The presence of Type II boundaries significantly reduced the resistance to stress corrosion cracking (SCC) and formed intergranular cracking under simulated reactor coolant conditions. Constant extension rate tensile (CERT) tests were performed on the notched tensile specimens in 300 C water at two extension rates, 3 10 4 and 1 10 6 mm/s. A fast CERT test can be regarded to have no contribution of corrosion, and its results can be used as standards for comparison. In the slow CERT tests, the ductility losses of round-bar specimens with a circumferential notch at various regions in the weld metal were ranked accordingly. The relative susceptibility to SCC in terms of the ductility loss in increasing order of severity was as follows: the undiluted weld metal, the transition zone and the weld interface. SEM fractographic observations were consistent with the SCC results, i.e., an increased ductility loss or SCC susceptibility was associated with more brittle fractures. [doi:10.2320/matertrans.M2010294]

Journal ArticleDOI
TL;DR: In this paper, the effects of Zn-based alloys coating (Zn, Al-Zn and Al-Mg Zn) on the bondability of steel/aluminum alloy dissimilar metals joints were evaluated, in order to achieve strength in lower welding current.
Abstract: The effects of Zn-based alloys coating (Zn, Al-Zn and Al-Mg-Zn) on the bondability of steel/aluminum alloy dissimilar metals joints were evaluated, in order to achieve strength in lower welding current. In the joint with Zn-based alloys insert, the oxide film on the aluminum alloy was sufficiently removed through eutectic reaction of Zn-based alloys and aluminum. In the joint with Zn-coated steel (GI), higher welding current is necessary to discharge the zinc coating and the oxide film from the bonding interface sufficiently. The thinner aluminum plate after welding and the thick reaction layer cause the decrease of cross tensile strength in the joints with no coating steel (SPCC) and Al-Zn-coated steel. Using Al-Mg-Zn-coated steel, higher strength was achieved in a lower welding current. This is because Al-Mg-Zn-coating melted at lower temperature than Zn and Al-Zn-coating, and the removal of the coating material and the oxide film on the aluminum alloy were sufficiently performed in the lower welding current.


Journal ArticleDOI
TL;DR: In this article, an aluminum plate was placed over a steel plate and a rotating welding tool was inserted into the aluminum plate, and the tip of the tool was dwelled above the aluminum/steel interface.
Abstract: Lap joining of a pure aluminum plate and a low carbon steel plate was performed using friction stir spot welding. The aluminum plate was placed over the steel plate, a rotating welding tool was inserted into the aluminum plate, and the tip of the tool was dwelled above the aluminum/steel interface. Dwell time was controlled in the range of 0 to 120 seconds. The microstructure of the welding interface was examined by optical microscopy and scanning electron microscopy. Chemical composition analysis was carried out by energy dispersive X-ray spectroscopy. Welding was achieved for all dwell times. Refined grains were formed by plastic flow in the aluminum matrix close to the welding interface. Intermetallic compound layer was produced along the welding interface. Precise backscattered electron image observation and energy dispersive X-ray spectroscopy analysis revealed that the intermetallic compound layer consisted of an Al13Fe4 phase layer and an Al5Fe2 phase layer. The thickness of the layers increased in proportion to the square root of the dwell time. The parabolic coefficient K was 1.30×10−14 and 6.06×10−13 m2/s for the Al13Fe4 layer and the Al5Fe2 layer, respectively.

Journal ArticleDOI
TL;DR: In this article, the authors investigated metal jet emission and weld interface formation in impact welding for similar-and dissimilar-metal lap joints for various plate thicknesses, collision velocities and collision angles.
Abstract: Metal jet emission and weld interface formation in impact welding were investigated for similar- and dissimilar-metal lap joints. Numerical simulation of oblique collision between metal plates was performed using smoothed particle hydrodynamics (SPH) method for various plate thicknesses, collision velocities, and collision angles. Metal jet emission and formation of the characteristic wavy weld interface in impact welding were reproduced successfully. The composition of the metal jet was governed by the degree of relative density difference between two metals. When the density difference was large, such as Al/Cu and Al/Ni lap joints, the metal jet was mainly composed of the metal component with lower density, Al. On the other hand, when the density difference was small or zero, such as for Cu/Ni and Al/Al lap joints, the metal jet was composed of both metal components. Several types of lap joints were fabricated by magnetic pulse welding (MPW). Metal jets emitted from Al/Cu and Cu/Al lap joints were collected, and their components were analyzed by X-ray diffraction. The microstructure of the weld interface was also examined. The experimental results were in good agreement with the simulation results.

Journal ArticleDOI
TL;DR: In this paper, the authors examined how the strain rate affects the room-temperature tensile behavior of hydrogen-charged 316L stainless steels and found that a softening phenomenon was observed in the hardening behavior of the H-charged and homogenized specimen at a strain rate of 2 � 10 � 3 /s.
Abstract: This study examined how the strain rate affects the room-temperature tensile behavior of hydrogen-charged 316L stainless steels. A hightemperature homogenization treatment was applied to the specimens after hydrogen charging and copper electroplating to remove the hydrogen concentration gradient. A softening phenomenon was observed in the hardening behavior of the H-charged and homogenized specimen at a strain rate of 2 � 10 � 3 /s. The observation was further confirmed by an inspection of the fracture surface of the tensile test specimen. [doi:10.2320/matertrans.M2010273]

Journal ArticleDOI
TL;DR: In this paper, the authors show that the quench sensitivity is related to dispersoid density as well as to the enthalpy related to the precipitation of Mg-Si phase measured by DSC.
Abstract: In high strength 6000 series alloys dispersoids that form during heating to the homogenization temperature are used to improve fracture toughness and suppress grain growth during the extrusion process. However, these dispersoids can act as heterogeneous nucleation sites for nonhardening Mg-Si precipitates if quenching after extrusion is delayed. This leads to a reduced level of Mg and Si in solid solution and hence lower achievable strength and hardness. This phenomenon is called quench sensitivity. In this study, the hardening response of several 6000 series aluminium alloys is related to microstructural features, especially dispersoid density. Therefore, the alloys were quenched at varying rates after extrusion and age hardened to peak strength. Quench sensitivity is related to dispersoid density as well as to the enthalpy related to the precipitation of Mg-Si phase measured by DSC. The results suggest that in alloys containing dispersoids, quench sensitivity is primarily determined by the number density of dispersoids. However, effects associated with elements in solid solution cannot be ruled out. TEM investigations suggest that not only the general reduction of Mg and Si is responsible for the reduced mechanical properties, but that an inhomogeneous distribution of hardening precipitates might be another determining factor. [doi:10.2320/matertrans.L-MZ201111]

Journal ArticleDOI
TL;DR: In this article, the dislocation densities in 10Cr-5W low-carbon steel that containing carbon content are determinedd from X-ray line analysis based on the modified Williamson-Hall and Warren-Averbach methods.
Abstract: Dislocation densities in 10Cr-5W low-carbon steel that containing carbon content is 0.02C, 0.03C, 0.09C and 0.13C mass% were determinedd from X-ray line analysis based on the modified Williamson-Hall and Warren-Averbach methods. In the as-quenched state the dislocation density in the martensite phase increased with increasing carbon content for these low-carbon steels.

Journal ArticleDOI
TL;DR: In this paper, a model was built to study the rule of glancing angle deposition, which is called the hemisphere model and is convenient to describe how the experimental conditions influence morphology of the nanostructures prepared by GLAD.
Abstract: A model was built to study the rule of glancing angle deposition. This model, which is called hemisphere model, is convenient to describe how the experimental conditions influence morphology of the nanostructures prepared by GLAD. Influence of experiment conditions such as incidence angle, incidence rate, substrate temperature, and substrate rotation rate are theoretical analyzed by the hemisphere model, and validated respectively by amount of experiments. As an application of the model, metals of different melting points were deposited into coherent multi-section nanorods by adjusting substrate temperature. [doi:10.2320/matertrans.M2010342] (Received September 29, 2010; Accepted December 8, 2010; Published February 2, 2011)

Journal ArticleDOI
Guangming Xie1, Zongan Luo1, Guanglei Wang1, Liang Li1, Guodong Wang1 
TL;DR: In this article, the microstructure characteristic and properties of the clad interface were investigated in detail, and a small amount of very fine oxide particles (diameter < 0.5 μm) can be found at the interface, and no obvious defects were observed.
Abstract: 304 austenite stainless steel plate and HSLA steel plate were subjected to vacuum rolling cladding (VRC). The microstructure characteristic and properties of the clad interface were investigated in detail. During the VRC process, the clad interface was held at a high vacuum all the time, resulting in significantly decreased oxidation at the interface. A small amount of very fine oxide particles (diameter<0.5 μm) can be found at the clad interface, and no obvious defects were observed. The remarkable diffusion of Ni and Cr elements led to the formation of a transition zone with high hardness. The shear strength of the clad interface was as high as 487 MPa, and the fracture occurred at the HSLA steel near the transition zone. No cracks were found at the clad interface after the 180° bending tests with both outside and inside manners.

Journal ArticleDOI
TL;DR: In this paper, the possibility of recovering precious metals and other valuable metals from wastewaters by various traditional metallurgical processes such as cementation, neutralization and reduction, were investigated.
Abstract: Generally, trace precious metals remaining in wastewaters generated from the refining process of precious metals are not recovered, due to a relatively high processing cost as well as various technical problems. Recovery of precious metals from wastewaters is very important for the conservation of resources and the protection of environment. However, wastewaters containing a large amount of ammonium ion (NH4 þ ) cannot be treated by general neutralization operation, due to formation of metal ammine complexes with increasing pH. In this study, the possibility of recovering precious metals and other valuable metals from wastewaters by various traditional metallurgical processes such as cementation, neutralization and reduction, were investigated. A recovery of 99% Copper (Cu), 96% Palladium (Pd), and 85% Gold (Au) by cementation using Iron (Fe) powder, and 99.6% Cu, 99.5% Pd by cementation using Aluminum (Al) powder was achieved. However, complete recovery of all valuable metals by a one-step cementation process was not possible. On the other hand, precious metals and other valuable metals including Copper and Indium, etc., were precipitated by combining neutralization, deammoniation and reduction processes. Results showed that the recovery of Platinum (Pt) in the reduction process was improved by adding deammoniation step. Finally, precious metals are concentrated in the crude copper metal by fusion process. The recovery of Au, Ag, Pd was more than 91%, and that of Pt was about 71%. [doi:10.2320/matertrans.M2010432]

Journal ArticleDOI
TL;DR: In this paper, thermal desorption spectroscopy of pure aluminum foils with 99.99% purity with different amount of blisters has been used to investigate hydrogen trapping states.
Abstract: Hydrogen trapping states in pure aluminum foils with 99.99% purity with different amount of blisters have been investigated by means of thermal desorption spectroscopy. Three peaks are seen in the spectra, where the amount of hydrogen from the third peak at the highest temperature range increases with increasing in the volume fraction of the blisters. Hence, the third peak is revealed to arise from the hydrogen in the blisters. The desorption energy of hydrogen released from the blisters is 76.3 kJ/mol. On the other hand, the first peak is inferred to be due to the hydrogen diffusing with vacancy, considering the diffusion distance of the vacancy as well as untrapped hydrogen atom.

Journal ArticleDOI
TL;DR: In this paper, carbonates and hydroxides were investigated as foaming agents for the production of Al-Si-Cu alloy foams by the powder metallurgy (PM) route.
Abstract: Metallic foams are commonly produced using hydride foaming agents Carbonates are safer to handle than hydrides; however, their use in the powder metallurgy (PM) route to obtaining a fine and homogenous cell structure has not been evaluated In this study, carbonates and hydroxides were investigated as foaming agents for the production of Al-Si-Cu alloy foams by the PM route The thermal decomposition behavior of the foaming agents was evaluated in conjunction with the cell structure of the aluminum foams produced From the results, it was clarified that a foaming agent that began decomposing after the matrix melted is required to obtain a fine and homogenous cell structure The TiH2 foam formed under similar conditions was obviously different and had a coarse and rounded cell structure MgCO3 and CaMg(CO3)2 were selected as suitable foaming agents for the Al-Si-Cu alloy Once expanded, the CaMg(CO3)2 foam had a specific gravity of 119 and a homogeneous, fine and spherical cell structure [doi:102320/matertransM2010401]

Journal ArticleDOI
Jin-Kyu Lee1, Shae K. Kim1
TL;DR: In this paper, the ignition resistance for CaO added Mg-Al alloys was examined by DTA for quantitative data, furnace chip ignition test for the safety of machined chips and torch ignition test to safety of products.
Abstract: The ignition resistance was investigated for CaO added Mg-Al alloys. The ignition resistance was examined by DTA for quantitative data, furnace chip ignition test for the safety of machined chips and torch ignition test for safety of products. The ignition resistances under all conditions greatly increased by CaO addition. AES depth profile was performed to evaluate the ignition resistance in terms of surface oxide stability. In the case of Mg-Al alloy without CaO, there was the thick and porous MgO oxide layer on the surface. The depth profile for CaO added Mg-Al Mg alloys indicated that the surface consisted of the thin and dense oxide layer mixed with MgO and CaO. [doi:10.2320/matertrans.M2010397]

Journal ArticleDOI
TL;DR: In this article, two types of nanoclusters, namely Cluster (1) and Cluster (2), play a strongly important role in the bake-hardening (BH) response in Al-Mg-Si alloys.
Abstract: Two types of nanoclusters, ie Cluster (1) and Cluster (2), play a strongly important role in the bake-hardening (BH) response in Al-Mg-Si alloys Different formation behaviors of two types of nanoclusters were studied by means of hardness, differential scanning calorimetry (DSC), electrical resistivity measurement, transmission electron microscopy (TEM) and high resolution TEM observation in the both Cu-free and Cu-added Al-Mg-Si alloys As the results, Cluster (1) formed during natural aging at room temperature causes a deleterious effect, whereas Cluster (2) formed by the pre-aging at 100°C is effective for the suppression of the negative effect on the two-step aging behavior of the both Cu-free and Cu-added alloys On the other hand, the microalloying of Cu strongly affects the nanocluster formation due to the strong interaction with Mg, Si atoms and vacancies The first-principle calculation for the two-body interaction energies provides quite useful information to understand the early stage of the phase decomposition The effects of nanoclusters and the Cu addition on the age-hardening behaviors of Al-Mg-Si alloys are discussed based on the multi-step age-hardening phenomena

Journal ArticleDOI
TL;DR: In this paper, vanadium is distributed between eutectic M7C3 carbide and the matrix, but its content in carbide is considerably higher than vanadium in high chromium iron.
Abstract: Experimental results indicate that vanadium affects the solidification process in high chromium iron. Vanadium is distributed between eutectic M7C3 carbide and the matrix, but its content in carbide is considerably higher. Also, this element forms vanadium carbide. TEM observation reveals that vanadium carbide present in examined Fe-Cr-C-V alloys is being of M6C5 type. DTA analysis found that with increasing vanadium content in tested alloys, liquidus temperature is decreasing, while eutectic temperature is increasing, i.e. the solidification temperature interval reduces. The narrowing of the solidification temperature interval and the formation of larger amount of vanadium carbides, as a result of the increase in the vanadium content of the alloy, will favour the appearance of a finer structure. In addition, the phases volume fraction will change, i.e. the primary γ-phase fraction will decrease and the amount of M7C3 carbide will increase.

Journal ArticleDOI
TL;DR: A comparison of theoretical models for electron-phonon coupling that is substantially associated with nonequilibrium energy transport in thin gold films irradiated by femtosecond pulse lasers is reported in this article.
Abstract: This study reports on a comparison of theoretical models for electron-phonon coupling that is substantially associated with nonequilibrium energy transport in thin gold films irradiated by femtosecond pulse lasers. Three published electron-phonon coupling models were analyzed with the use of a well-established two-temperature model to describe non-equilibrium energy transport between electrons and phonons. Based on the numerical results, at lower fluence, all models showed nearly similar tendencies, whereas at higher fluence, constant electronphonon coupling forced unrealistically long electron-phonon equilibration times and spatially long diffusive regions as it failed to intrinsically consider the effect of a high number density of excited d-band electrons. Even at higher fluence, however, both Lin’s and Chen’s models yielded physically reasonable results, showing converging electron-phonon equilibration times and steep gradients in the spatial lattice temperature profiles at higher laser fluence. In particular, Lin’s model predicts nonlinear characteristics of heat capacity and lattice temperature with respect to laser fluence better than Chen’s model. Moreover, the electron-phonon relaxation time increased with laser fluence, whereas at laser fluence greater than 0.05 J/cm 2 , the thermal equilibrium time was nearly independent of the laser fluence. Thus, it was concluded that Lin’s model better predicted the electron-phonon coupling phenomena in thin metal films irradiated by ultra-short pulse lasers. [doi:10.2320/matertrans.M2010396]

Journal ArticleDOI
TL;DR: In this paper, the reduction of tin oxide by hydrogen in the temperature range of 773� 1023 K and the hydrogen partial pressure of 30:4� 101:3 kPa was investigated.
Abstract: This study deals with the reduction of tin oxide by hydrogen in the temperature range of 773� 1023 K and the hydrogen partial pressure of 30:4� 101:3 kPa. It aims to investigate the kinetics of the reaction between tin oxide and hydrogen. The hydrogen reduction of tin oxide is to be related with the efforts to extract tin metal with decreasing the emission of carbon dioxide which causes global warming. The experiments were carried out under isothermal condition in hydrogen atmosphere using TGA equipment. The reduction rate of tin oxide to tin metal by hydrogen was found to be relatively fast under the whole conditions until the reduction ratio of SnO2 approaches to about 0.95. As an example, at 1023 K under a hydrogen partial pressure of 101.3 kPa, almost 100% of tin oxide was reduced to tin metal in 10 min. The nucleation and growth model yielded a satisfactory fit to these experimental data. The reaction was first order with respect to hydrogen partial pressure and had an activation energy of 62.5 kJ/mol (15.0 kcal/mol). [doi:10.2320/matertrans.M2011118]

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a model for anisotropy and texture analysis of materials, which is based on the key laboratory for Mechanical Behavior of Materials at the University of Northeastern University in China.
Abstract: Institute of Materials Physics and Chemistry, College of Sciences, Northeastern University, P.O. Box 104, No. 3-11, Wenhua Road, Shenyang, 110004, P. R. China State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, P. R. China Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, No. 3-11, Wenhua Road, Shenyang 110004, P. R. China