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ISSN 1005-0302
CN 21-1315/TG
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      20 December 2014, Volume 30 Issue 12 Previous Issue    Next Issue
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    Orginal Article
    Ultralong and Mesoporous ZnO and γ-Al2O3 Oriented Nanowires Obtained by Template-assisted Hydrothermal Approach
    Carminna Ottone, Vivian Farí, as Rivera, Marco Fontana, Katarzyna Bejtka, Barbara Onida, Valentina Cauda
    J. Mater. Sci. Technol., 2014, 30 (12): 1167-1173.  DOI: 10.1016/j.jmst.2014.11.005
    Abstract   HTML   PDF
    Highly mesoporous ZnO and γ-Al2O3 nanowires (NWs) are both synthesized by a hydrothermal method using commercially available porous anodic aluminium oxide (AAO) as template. AAO membrane acts as template for ZnO NWs and both as template and precursor for γ-Al2O3 NWs. The formation of intermediate phases of porous Zn6Al2(OH)16CO3 and boehmite (γ-AlOOH) were observed, both occurring during the hydrothermal synthesis of porous ZnO and γ-Al2O3 NWs, respectively, and disappearing after annealing at 600 °C. This novel template-assisted hydrothermal process leads to the formation of porous ZnO and γ-Al2O3 NWs (specific surface area of 192 m2 g-1 and 263 m2 g-1, respectively), showing pore sizes around 4 nm in diameter. The influence of the reaction parameters on the nanostructure morphology was also investigated. A ZnO seed layer, deposited on the AAO channels prior to the hydrothermal synthesis, leads to more compact ZnO nanowires (99 m2 g-1) protecting the AAO host from the chemical attack of the precursor solution.
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    Oxygen Permeation and Stability of Ce0.8Gd0.2O2-δ-PrBaCo2-xFexO5+δ Dual-phase Composite Membranes
    Bo Jiang, Hongwei Cheng, Longfei Luo, Xionggang Lu, Zhongfu Zhou
    J. Mater. Sci. Technol., 2014, 30 (12): 1174-1180.  DOI: 10.1016/j.jmst.2014.09.001
    Abstract   HTML   PDF
    Dual-phase membranes of 60 wt% Ce0.8Gd0.2O2-δ-40 wt% PrBaCo2-xFexO3-δ (0 ≤ x ≤ 2) were prepared by combined citrate and ethylene diamine tetraacetic acid (EDTA) complexing method. X-ray diffraction (XRD) results revealed the good chemical compatibility between ion-conducting phase CGO and electron-conducting phases PBC2-xFxO after sintering in air. The Fe ionic dopant had a significant effect on the phase structure stability and oxygen permeability under CO2 atmosphere, which was confirmed by XRD, thermogravimetry-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM) and oxygen permeation experiments. CGO-PBC0.5F1.5O dual-phase membrane demonstrated a stable oxygen permeation flux of 2.71 × 10-7 mol cm-2 s-1 with 50 mol% He/CO2 as the sweep gas at 925 °C, and this value was much higher than that of perovskite-type membranes. The rate-limiting step in the oxygen permeation process changed from the bulk diffusion to the surface oxygen exchange when the CGO-PBC0.5F1.5O membrane thickness decreased to 0.8 mm or less. Due to the high oxygen permeation fluxes and the excellent structural stability under CO2 atmosphere, the CGO-PBC0.5F1.5O membrane is a great potential candidate material for separating oxygen from air in the oxy-fuel combustion techniques.
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    Analysis of Surface Oxide Films Formed in Hydrogenated Primary Water on Alloy 690TT Samples With Different Surface States
    Zhiming Zhang, Jianqiu Wang, En-Hou Han, Wei Ke
    J. Mater. Sci. Technol., 2014, 30 (12): 1181-1192.  DOI: 10.1016/j.jmst.2014.09.002
    Abstract   HTML   PDF
    Oxidation of Alloy 690TT samples either manually ground to 400 and 1500 grit, mechanically polished, or electropolished was performed in a solution of 1500 × 10-6 B and 2.3 × 10-6 Li with 2.5 × 10-6 dissolved H2, at 325 °C and 15.6 MPa for 60 days. The oxide films grown on samples with different surface states were analyzed using various techniques. Results show that a triple-layered structure was formed after immersion: an outermost layer with large scattered oxide particles rich in Fe and Ni, an intermediate layer with small compact oxide particles rich in Cr and Fe for the ground surfaces and loose needle-like oxides rich in Ni for the polished surfaces, and an inner layer with continuous Cr-rich oxides. The surface state was found to affect not only the surface morphology, but also the corrosion rate. Grinding accelerated the growth of protective oxide films such that the ground samples showed a lower oxidation rate than the polished ones. Samples of ground Alloy 690TT showed superior resistance to intergranular attack (IGA).
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    Microstructure, Interface, and Properties of Multilayered CrN/Cr2O3 Coatings Prepared by Arc Ion Plating
    Chang-Ming Shi, Tie-Gang Wang, Zhi-Liang Pei, Jun Gong, Chao Sun
    J. Mater. Sci. Technol., 2014, 30 (12): 1193-1201.  DOI: 10.1016/j.jmst.2014.05.010
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    There has been much interest in developing multilayered or nanolayered physical vapor deposition (PVD) coatings identified as a group of promising protective coatings for their excellent mechanical properties and corrosion resistance. In this study, the multilayered CrN/Cr2O3 coatings with different bilayer periods (Λ) were synthesized on the polished high speed steel substrates from a Cr target with the alternative atmosphere of pure nitrogen and pure oxygen by arc ion plating (AIP) technique. The results revealed that the microstructure, morphologies and properties of the multilayered coatings were strongly influenced by the bilayer period (Λ). There were two kinds of interfaces in the multilayered CrN/Cr2O3 coatings: the sharp ones and the blurry ones. With reducing the value of Λ, the macro-particles densities decreased gradually, whereas the coating microhardness, adhesive strength and wear resistance first increased, and then decreased slightly or remained stable as the bilayer period Λ < 590 nm. The multilayered CrN/Cr2O3 coating with the bilayer period Λ of 590 nm possessed the best comprehensive properties, namely the highest microhardness, the strongest adhesion, and the lowest wear rate.
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    Microstructure and Mechanical Properties of Multilayer-textured 2D Carbon/Carbon Composites
    Yan Jia, Kezhi Li, Shouyang Zhang, Lei Li, Junjie Ren
    J. Mater. Sci. Technol., 2014, 30 (12): 1202-1207.  DOI: 10.1016/j.jmst.2014.03.026
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    Two-dimensional (2D) carbon/carbon (C/C) composites with multilayered texture, especially with different thickness of high-textured (HT) pyrocarbon layer, were prepared by isothermal, isobaric chemical vapor infiltration (CVI) technique. The influence of matrix microstructure on mechanical properties of C/C composites was investigated by polarized light microscopy, scanning electron microscopy and three-point bending test. The results show that the samples with multilayer-textured pyrocarbon matrix own a higher flexural strength than the one with pure medium-textured structure, which is attributed to multiple crack deflection and interfacial sliding between different textured pyrocarbon layers and between sub-layers within HT layer. The increase in thickness of HT pyrocarbon layer improves the plasticity of the samples and renders the fracture in pseudo-plastic behavior.
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    Utilization of Coal Fly Ash for the Production of Glass-ceramics With Unique Performances: A Brief Review
    Shuming Wang, Caixing Zhang, Jundan Chen
    J. Mater. Sci. Technol., 2014, 30 (12): 1208-1212.  DOI: 10.1016/j.jmst.2014.10.005
    Abstract   HTML   PDF
    Coal fly ash is an industrial by-product generated during the combustion of coal for energy production. Due to the increasing annual consumption of coal power and the serious potential environmental threats of coal fly ash, a considerable amount of research on the utilization of coal fly ash has been undertaken worldwide. Vitrification seems to be one of the most promising options for reusing this industrial waste. This paper presents a short overview of the production of unique high performance glass-ceramics using coal fly ash as a raw material. A detailed description of the methodologies for the synthesis of glass-ceramics from coal fly ash and the principal crystal phases, corresponding property and possible usage of those materials are introduced. Investigations revealed that converting coal fly ash into high performance glass-ceramic materials is a promising new approach to improve the utilization of this industrial by-product. This conversion not only alleviates the problems with disposal but also converts a waste material into a high value-added marketable commodity.
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    Role of Heavy Metal Ions in the Formation of Oxyfluoride Glasses and Glass Ceramics
    Min Liu, Lijuan Zhao, Yan Liu, Zijian Lan, Lifen Chang, Yiming Li, Hua Yu
    J. Mater. Sci. Technol., 2014, 30 (12): 1213-1216.  DOI: 10.1016/j.jmst.2014.02.003
    Abstract   HTML   PDF
    In order to investigate the influence of different heavy metal ions on the formation of the oxyfluoride glasses and glass ceramics, samples with different PbF2/CdF2 ratios have been prepared by the melting quenching and thermal treatment method. The different effects of Pb2+ and Cd2+ on the glass network structure are investigated by FTIR and Raman spectra. During the formation of glass network structure, Pb2+ prefers to break the Si-O-Si bond and subsequently bond to F- for charge compensation, and Cd2+ prefers to break the Si-O-Al bond and is surrounded by O2-. Pb2+ and F- gather together and form the fluoride nanocrystals, while Cd2+ remains in oxide matrix after thermal treatment. Introduction of proper CdF2 is important to adjust and control the glass network structure and crystallization process in the fabrication of the transparent glass ceramics.
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    Porosity and Oxide Layer Dependence of Thermal Shock Behavior of Porous Silicon Nitride Ceramics
    Xuefeng Lu, Yin Wei, Hongjie Wang, Jiangbo Wen, Jun Zhou, Jinpeng Fan
    J. Mater. Sci. Technol., 2014, 30 (12): 1217-1222.  DOI: 10.1016/j.jmst.2014.11.004
    Abstract   HTML   PDF
    A water-quenching technique has been adopted to evaluate thermal shock fracture and fatigue behaviors of porous Si3N4 ceramics in an air atmosphere. The high-porosity Si3N4 ceramics exhibit a higher strength retention and a better resistance to thermal shock fatigue because of its role of the pores as crack arresters. A dense and coherent surface oxide layer leads to a significant benefit in residual strength during thermal fatigue, however, an increased fatigue number to 30th cycle cannot cause a further influence although a thicker oxide layer presents, which is attributed to holes defect and disappearance of part intergranular phase.
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    Oxidation Behaviors of C-ZrB2-SiC Composite at 2100 °C in Air and O2
    Zhongwei Zhang, Cewen Nan, Jingjun Xu, Zenghua Gao, Meishuan Li, Junshan Wang
    J. Mater. Sci. Technol., 2014, 30 (12): 1223-1229.  DOI: 10.1016/j.jmst.2014.04.013
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    Bonding Interface of W-CuCrZr Explosively Welded Composite Plates for Plasma Facing Components
    Congxiao Sun, Shuming Wang, Wenhao Guo, Weiping Shen, Changchun Ge
    J. Mater. Sci. Technol., 2014, 30 (12): 1230-1234.  DOI: 10.1016/j.jmst.2014.11.014
    Abstract   HTML   PDF
    In order to realize the effective jointing of tungsten and CuCrZr alloys manufactured for plasma facing components (PFCs), explosive welding is employed for its some unique advantages. Different welding characteristics were investigated in this study. The interfacial waveform of the welded plates changed periodically from flat-wavelet to a large wave and finally to a stable wave, which began with the detonation point. The bonding strength of the specimens is higher than 32.9 MPa. Welding hardening and the formation of microcracks occurred at the interface zone. The results demonstrate that the joining reliabilities need to be improved in order to meet the need of applications involving the use of explosive welding to fabricate tungsten-based PFCs.
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    Different Diffusion Behavior of Cu and Ni Undergoing Liquid-solid Electromigration
    M.L. Huang, Z.J. Zhang, H.T. Ma, L.D. Chen
    J. Mater. Sci. Technol., 2014, 30 (12): 1235-1242.  DOI: 10.1016/j.jmst.2014.11.013
    Abstract   HTML   PDF
    The diffusion behavior of Cu and Ni atoms undergoing liquid-solid electromigration (L-S EM) was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 × 103 A/cm2 at 250 °C. The flowing direction of electrons significantly influences the cross-solder interaction of Cu and Ni atoms, i.e., under downwind diffusion, both Cu and Ni atoms can diffuse to the opposite interfaces; while under upwind diffusion, Cu atoms but not Ni atoms can diffuse to the opposite interface. When electrons flow from the Cu to the Ni, only Cu atoms diffuse to the opposite anode Ni interface, resulting in the transformation of interfacial intermetallic compound (IMC) from Ni3Sn4 into (Cu,Ni)6Sn5 and further into [(Cu,Ni)6Sn5 + Cu6Sn5], while no Ni atoms diffuse to the opposite cathode Cu interface and thus the interfacial Cu6Sn5 remained. When electrons flow from the Ni to the Cu, both Cu and Ni atoms diffuse to the opposite interfaces, resulting in the interfacial IMC transformation from initial Cu6Sn5 into (Cu,Ni)6Sn5 and further into [(Cu,Ni)6Sn5 + (Ni,Cu)3Sn4] at the anode Cu interface while that from initial Ni3Sn4 into (Cu,Ni)6Sn5 and further into (Ni,Cu)3Sn4 at the cathode Ni interface. It is more damaging with electrons flowing from the Cu to the Ni than the other way.
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    Mechanical Properties and Microstructure of 6082-T6 Aluminum Alloy Joints by Self-support Friction Stir Welding
    Long Wan, Yongxian Huang, Weiqiang Guo, Shixiong Lv, Jicai Feng
    J. Mater. Sci. Technol., 2014, 30 (12): 1243-1250.  DOI: 10.1016/j.jmst.2014.04.009
    Abstract   HTML   PDF
    The majority of this research has concentrated on developing the self-support friction stir welding (SSFSW) tool which consists of a big concave upper shoulder and a small convex lower shoulder, and procedures for making reliable welds in aluminum hollow extrusion. The 5-mm-thick 6082-T6 aluminum alloy was self-support friction stir welded at a constant tool rotation speed of 800 r/min. The effect of welding speed on microstructure and mechanical properties was investigated. The results of transverse tensile test indicated that the tensile strength of joints increased and the elongation decreased with increasing welding speed. The whole values of microhardness of SSFSW joints increased with increasing welding speed from 10 to 200 mm/min. The defect-free joints were obtained at lower welding speeds and the tensile fracture was located at the heat-affected zone (HAZ) adjacent to the thermo-mechanically affected zone (TMAZ) on the advancing side. The investigation of the flow pattern of the softened metal around the SSFSW tool revealed that the flow pattern of the softened metal was driven by two shoulders and the stir pin. The failure of specimens in tension presented the ductile fracture mode.
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    Improving Corrosion Resistance of Friction Stir Welding Joint of 7075 Aluminum Alloy by Micro-arc Oxidation
    Yue Yang, Leilei Zhou
    J. Mater. Sci. Technol., 2014, 30 (12): 1251-1254.  DOI: 10.1016/j.jmst.2014.07.017
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    Hot ductility, stress-strain behavior and high temperature tensile fracture behavior of wrought 316LN stainless steel were investigated. Hot tensile tests were carried out on a Gleeble 1500D thermal simulator system at a strain rate of 0.5 s-1 over the temperature range 650-1300℃. The percentage reduction of area (RA) decreased with the increasing deformation temperature over the range of 650-850℃, and then starting from 850℃, it began to increase dramatically with values over 85% above 1000℃. When the deformation temperature comes to 1300℃, RA decreased sharply as a result of the grain coarsening due to over-heating. With the help of optical microscopy, dynamic recrystallization (DRX) was observed for the steel deformed at temperature over 1000℃. The enhancement of ductility induced by DRX was considered to play an important role in inhibition of the crack propagation. The high temperature tensile failure process of 316LN includes the nucleation, growth, and aggregation of microscopic cavities. The SEM/EDS results show that the sulfide and alumina at grain boundaries may be responsible to the formation process of cracks.
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    Effects of Y on the Microstructure, Mechanical and Bio-corrosion Properties of Mg-Zn-Ca Bulk Metallic Glass
    Jingfeng Wang, Yang Li, Song Huang, Yiyun Wei, Xingfeng Xi, Kaiyong Cai, Fusheng Pan
    J. Mater. Sci. Technol., 2014, 30 (12): 1255-1261.  DOI: 10.1016/j.jmst.2014.11.007
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    The micro-alloying effects of Y on the microstructure, mechanical properties, and bio-corrosion behavior of Mg69-xZn27Ca4Yx (x = 0, 1, 2 at.%) alloys were investigated through X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests. The Mg69Zn27Ca4 alloy was found to be absolutely amorphous, and its glass-forming ability decreased with the addition of Y. The Mg68Zn27Ca4Y1 alloy exhibited an ultrahigh compressive strength above 1010 MPa as well as high capacity for plastic strain above 3.1%. Electrochemical and immersion tests revealed that these Y-doped Mg-Zn-Ca alloys had good bio-corrosion resistance in simulated body fluid (SBF) at 37 °C. The results of the cytotoxicity test showed high cell viabilities for these alloys, which means good bio-compatibility.
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    Crystallization of Al-based Amorphous Alloys in Good Conductivity Solution
    Yonggang Wang, Yan Liu, Yingjie Li, Bang An, Guanghui Cao, Shifeng Jin, Yimin Sun, Weimin Wang
    J. Mater. Sci. Technol., 2014, 30 (12): 1262-1270.  DOI: 10.1016/j.jmst.2014.10.003
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    The corrosion-induced crystallization of Al94-xNixGd6 (x = 6 and 10, in at.%) metallic glasses as well as phase separation, oxidation and cracking in good conductivity solution has been investigated by various techniques. The transmission electronic microscopy (TEM) result reveals that crystalline intermetallics and oxides present on the electrochemically thinned hole edge, and the phase separation occurs in the matrix of the as-spun ribbons with the circumferential speed Rc of 29.3 m/s. In addition, the bending and cracking of the samples occur after corrosion. The influence of Ni content on the phase separation, bending and cracking can be explained by the fact that the percolation of the backbone clusters in the amorphous alloy melts and glasses is enhanced by increasing the composition of Ni.
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    Effect of Si Content on Dynamic Recrystallization of Al-Si-Mg Alloys During Hot Extrusion
    Yuna Wu, Hengcheng Liao, Jian Yang, Kexin Zhou
    J. Mater. Sci. Technol., 2014, 30 (12): 1271-1277.  DOI: 10.1016/j.jmst.2014.07.011
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    By using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), the effect of Si content on microstructure characteristics of three as-extruded Al-Si-Mg alloys was investigated. Results showed that the density of coarse Si particles played a critical role in dynamic recrystallization. Dynamic recrystallization rarely occurred in S1 alloy with less Si content; however, it happened in the Si-rich zones in S2 alloy with a medium Si content. And a mature recrystallization was observed in S3 alloy with high Si content. Although deformation was carried out at high temperature, particle-stimulated dynamic recrystallization occurred in Si-rich zones.
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    Microstructure and Wear Resistance of in situ Formed Duplex Coating Fabricated by Plasma Nitriding Ti Coated 2024 Al Alloy
    Fanyong Zhang, Mufu Yan
    J. Mater. Sci. Technol., 2014, 30 (12): 1278-1283.  DOI: 10.1016/j.jmst.2013.10.032
    Abstract   HTML   PDF
    In this study, plasma nitriding was carried out on pure titanium film coated 2024 Al alloy to improve its surface mechanical property. Ti film with the thickness of 3.0 μm was firstly fabricated by means of magnetron sputtering method. Then, the Ti coated specimen was subjected to plasma atmosphere comprising 40% N2-60% H2 at 430 °C for 8 h. The microstructures of the nitrided specimens were characterized by X-ray diffraction and scanning electron microscopy. Microhardness tester and pin-on-disc tribometer were used to test the mechanical properties of the untreated and nitrided specimen. The results showed that the surface of the nitrided specimen was composed of three layers (i.e. the outside nitride TiN0.3 layer, the middle Al3Ti layer and the inside Al18Ti2Mg3 layer). The surface hardness and wear resistance of 2024 Al alloy were increased simultaneously by duplex treatment. The untreated specimen exhibited severe adhesive wear while the nitrided one behaved in middle abrasive wear.
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    Geometrical Scale-Sensitive Fatigue Properties of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloys With α/β Lamellar Microstructures
    B. Zhang, Z.M. Song, L.M. Lei, L. Kang, G.P. Zhang
    J. Mater. Sci. Technol., 2014, 30 (12): 1284-1288.  DOI: 10.1016/j.jmst.2014.07.012
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    Fatigue properties of the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy sheets containing different numbers of α/β Widmanstätten colonies in the thickness direction of the sheets were investigated by tension-tension fatigue testing. It is found that fatigue properties of the Ti alloy either in low- or high-stress amplitude regimes become more sensitive to the sheet thickness of the Ti alloy as the sheet thickness is comparable to the length scale of the Widmanstätten colonies. The basic mechanism of such length scale-sensitive fatigue properties in the Ti alloy was elucidated.
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    Effect of Hot Isostatic Pressing Conditions and Cooling Rate on Microstructure and Properties of Ti-6Al-4V Alloy from Atomized Powder
    Lei Xu, Ruipeng Guo, Chunguang Bai, Jiafeng Lei, Rui Yang
    J. Mater. Sci. Technol., 2014, 30 (12): 1289-1295.  DOI: 10.1016/j.jmst.2014.04.011
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    The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing (HIPping) were investigated. Optimized HIPping parameters of temperature range from 900 to 940 °C, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology (RSM) in this study.
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    Effect of Solidification Condition and Carbon Content on the Morphology of MC Carbide in Directionally Solidified Nickel-base Superalloys
    X.W. Li, L. Wang, J.S. Dong, L.H. Lou
    J. Mater. Sci. Technol., 2014, 30 (12): 1296-1300.  DOI: 10.1016/j.jmst.2014.06.010
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    Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40 × 10-6 to 320 × 10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into well-developed dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.
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    Rapidly Solidified Microstructure in Laser Alloyed Ni-Al Layer by TEM, STEM z-contrast and HRTEM Techniques
    Yue Yang, Jiandong Hu
    J. Mater. Sci. Technol., 2014, 30 (12): 1301-1303.  DOI: 10.1016/j.jmst.2014.11.002
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    In the present study, laser alloying of electroless Ni-P coating on aluminum substrate was conducted using Nd:YAG pulsed laser under the condition of 5.36 × 109 W/m2 in power density and 3.0 mm/s in scanning speed. The rapidly solidified microstructure in the alloyed layer was studied. The results showed that the alloying element distributed in the alloyed layer is inhomogeneous. The dendrite containing relatively high Ni was identified as Al3Ni phase and the areas between the dendrites are rich in Al content. Featureless with cell structure in Al-rich areas was firstly displayed by z-contrast image. Amorphous structure was revealed to exist in Al-rich areas.
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    Preparation and Properties of Asphalt Modified with a Composite Composed of Waste Package Poly(vinyl chloride) and Organic Montmorillonite
    Changqing Fang, Xiaolong Liu, Ruien Yu, Pei Liu, Wanqing Lei
    J. Mater. Sci. Technol., 2014, 30 (12): 1304-1310.  DOI: 10.1016/j.jmst.2014.11.001
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    A composite composed of waste package poly(vinyl chloride) (WPVC) and organic montmorillonite (OMMT) was prepared by coextrusion, which is used for modifying asphalt. The micromorphology of the WPVC/OMMT composite and its effect on the macroscopic properties of asphalt were studied using a fluorescent microscope and an X-ray diffractometer (XRD). The introduction of OMMT allows the WPVC to be good dispersed in the asphalt matrix, as demonstrated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis. The results indicate that asphalt modified by WPVC/OMMT composites with low OMMT content results in better high-temperature storage stability and physical properties of modified asphalt.
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    A Modified Cellular Automaton Model for the Quantitative Prediction of Equiaxed and Columnar Dendritic Growth
    Rui Chen, Qingyan Xu, Baicheng Liu
    J. Mater. Sci. Technol., 2014, 30 (12): 1311-1320.  DOI: 10.1016/j.jmst.2014.06.006
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    Since the characteristic of dendrite is an important factor determining the performance of castings, a two-dimensional cellular automaton model with decentered square algorithm is developed for quantitatively predicting the dendritic growth during solidification process. The growth kinetics of solid/liquid interface are determined by the local equilibrium composition and local actual liquid composition, and the calculation of the solid fraction increment is based on these two compositions to avoid the solution of growth velocity. In order to validate the developed model, quantitative simulations of steady-state dendritic features over a range of undercooling was performed and the results exhibited good agreement with the predictions of LGK (Lipton-Glicksman-Kurz) model. Meanwhile, it is demonstrated that the proposed model can be applied to simulate multiple equiaxed dendritic growth, as well as columnar dendritic growth with or without equiaxed grain formation in directional solidification of Al-Cu alloys. It has been shown that the model is able to simulate the growth process of multi-dendrites with various preferential orientations and can reproduce a wide range of complex dendritic growth phenomena such as nucleation, coarsening of dendrite arms, side branching in dendritic morphologies, competitive growth as well as the interaction among surrounding dendrites.
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