bluuebunny/crossref_metadata_2025 huggingface dataset:
MOD-Derived YBa2Cu3O7-δ Thin Films using a Fast Pyrolysis Process
Authors: Hao Wen Jia , Lu Yu Ming , Bai Chuan Yi , Liu Zhi Yong , Gao Bo , Cai Chuan Bing
Published: March 2013

In the present work, a fast pyrolysis process is developed for YBa2Cu3O7-δ (YBCO) films preparation with trifluroacetates metalorganic deposition technique (TFA-MOD). The decomposition of TFA salts as well as the surface morphology of pyrolyzed films is investigated with respect to the pyrolysis temperature and its heating rate. Two typical surface morphologies for the pyrolyzed films, being smooth or buckled, are revealed subjecting to the heating rate and film thickness, which related to the subsequent YBCO films property. Smooth and wrinkle-free pyrolyzed films are achieved by using this fast pyrolysis process with a heating rate as high as 5°C/min. The final crystallized YBCO films exhibit good performances with the superconducting transition temperature of 91 K and critical current density of 2.0 MA/cm2 at 77 K, suggesting a rapid, promising MOD route available for scale-up preparation of YBCO coated conductors.
Hydrothermal Synthesis and Morphology Evolution of Perovskite PbTiO3 Crystals with Different Lead Sources
Authors: Yin Si Min , Xu Gang , Ren Zhao Hui , Chao Chun Ying , Shen Ge , Han Gao Rong
Published: March 2013

Perovskite lead titanate crystals with various morphologies were successfully synthesized via a hydrothermal reaction route with different lead sources. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the phase composition and the morphology of the synthesized products. In order to investigate the effect of the lead source on the phase formation and morphology evolution of the synthesized pervoskite PbTiO3 crystals, PbO, PbF2, PbSO4 and Pb (CH3COO)3 ·3H2O, were used as starting precursor lead source introduced into the hydrothermal reaction system, respectively. Accordingly, perovskite PbTiO3 brken cubes, irregular particles, cubic particles, and microplates were obtained, respectively. Based on the experimental results, the effect of lead source was simply discussed.
Synthesis of Nano-WC by High-Energy Ball Milling
Authors: Dai Le Yang , Lin Shao Fen , Chen Jing Feng , Wang Wen Chun
Published: March 2013

Nanosized tungsten carbide (nanoWC) has been widely studied and applied in many industries as hard materials since it has good combination of high hardness and strength. Thermal mechanical alloying method consisting of high-energy ball milling and subsequent carbonization is a common synthetic approach to prepare nanoWC. In this paper, a special milling process has been reviewed, in which the dielectric barrier discharge plasma (DBDP) is introduced, for the preparation of nanoWC. The DBDP milling renders the W+C powders with specific flake-like structure possible owing to the cooperative effect of DBDP and mechanical milling. The obtained W+C powders are activated significantly within shortened milling period. Furthermore, pure nanoWC powders can be synthesized after subsequent carbonization at a significantly lowered temperature. DBDP milling is demonstrated to be an efficient way to synthesize nanoWC.
Effect of Poly Sodium-p-Styrenesulfonate on the Phase Formation and Morphology of the Hydrothermally Synthesized Bismuth Ferrite Powders
Authors: Yang Xin , Xu Gang , Ren Zhao Hui , Han Gao Rong , Shen Ge
Published: March 2013

Rhombohedral bismuth ferrite (BiFeO3) powders were hydrothermally synthesized by using C6H8BiNO7 and Fe (NO3)·5H2O as precursors, KOH as a mineralizer and poly sodium-p-styrenesulfonate (PSS) as an additive. The phase formation and morphology of the as-prepared powders were characterized by X-ray diffraction,raman spectroscopy, and field-emission scanning electron microscopy. In order to investigate the effects of PSS, a series of experiments were performed by changing the introduced amount of PSS and the hydrothermal reaction time. The results showed that the introduction of the PSS leads to the synthesized bismuth ferrite changes from the mixture of Bi2Fe4O9 and BiFeO3 to pure rhombohedral BiFeO3. Corresponding to the phase composition evolution, the particle morphology alters from nanosheets to microparticles. The magnetic properties of single-crystalline BiFeO3 powders were also characterized. Based on the experimental results, the phase formation mechanism of the rhombohedral BiFeO3 hydrothermally synthesized assisted with PSS was discussed.
Recent Progress on Research of Contact Resistance of Carbon Nanotubes
Authors: Yang Xiao Xia , An Li Bao , Ding Chao
Published: March 2013

This paper reviews the recent progress on the research of contact resistance of carbon nanotubes (CNTs), including the contact resistance between CNTs and electrodes/metals and that between CNTs. In particular, the current research advances in improving CNT contact resistance are presented. The challenges in improving CNT contact resistance are also addressed from a practical point of view. A thorough understanding of the electrical contact properties of CNTs helps to explore new methods to improve their contact resistance for full application of this unique group of materials.
Preparation of TiB2/TiN Nanocomposites by SP
Authors: Wang Ming Hui , Li Hua Jian , Jiang Wan
Published: March 2013

TiB2/TiN nanocomposites were in-situ fabricated by spark plasma sintering (SPS) technique using Ti and BN powders as starting materials. The phase constituents and microstructures of the samples were analyzed by X-ray diffraction (XRD) techniques, scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. The results showed that the average grain size of TiB2 and TiN was 1m and 300nm respectively. Furthermore, high resolution TEM analysis indicated that the as-prepared TiB2/TiN nanocomposites had very clean grain boundaries, and no amorphous phase or oxide layer was observed.
Application of Alumina-Magnesia Precast Blocks for LF Refining Ladle
Authors: Feng Hai Xia , Liu Jun , Wei Yi
Published: March 2013

The alumina-magnesia precast blocks developed in authors company have been successfully used in 90-ton LF refining with an average service life 80-85 heats to meet the smelting demand of low carbon steel and ultra low carbon steel. The observation of the residual blocks revealed that the section of the used blocks was divided into four layers from inside to the surface, i.e., slag layer, reaction layer, penetration layer and the original block. It has been found that there was a certain degree of structure spalling of the used blocks. The main factor of blocks damage may be due to the penetration and erosion of molten slag. The results of SEM microstructure analysis indicated that the calcium oxide (CaO) of high basicity slag easily penetrated into the blocks and formed CA6 phase, and then transformed into CA2 or C12A7 phases gradually with the decreasing content of alumina (Al2O3). It has been found that an annular distribution structure, and the silicon dioxide (SiO2) was easily lost together with slag and formed SiO2-rich part in the penetration layer due to the formation of low viscosity and low melting point phase of C2AS. A large number of-5um spinel particles (MgAl2O4) were synthesized at 1600~ 1700, which could absorb FeO, MnO and other impurities in slag to form composite spinel phase. It is believed that the high melting point phases intertwined to form a dense area which was beneficial to improve the bricks' slag resistances to penetration and corrosion
Preparation and Electrical Properties of Mn-Co-Ni-O Thin-Film for NTC Thermistors Application
Authors: Chen Xue Ying , Wang Lei , Xu Jin Bao , Bian Liang , Gao Bo
Published: March 2013

Mn-Co-Ni-O (Mn:Co:Ni=1.74:0.72:0.54, MCN) thin films with single cubic spinel structure were prepared on Si substrates by metal organic solution deposition (MOSD) method at different annealing temperatures. The effects of annealing temperature on the phase component, crystalline microstructure, surface morphology and electrical properties of the MCN thin films were studied. According to the results of x-ray diffraction pattern, the MCN thin film annealed at 650 had spinel structure. Observation with field emission scanning electron microscope (FE-SEM) on the MCN thin films showed that the grain size increased with increasing annealing temperature. The resistance measured at room-temperature was 18.143, 12.457, 2.435 and 3.141MΩ for the MCN thin films annealed at 650, 700, 750 and 800, respectively. The values of thermistor constant (B30/85) and activation energy (Ea) were in the range of 3260-4840K and 0.28-0.42eV, respectively.
Enhanced Humidity Stability of (Li,K,Na)NbO3-Based Lead-Free Piezoelectric Ceramics by Adding B2O3
Authors: Zhen Yu Hua , Wei Dai Shan , Jia Cui Ping , Ha Zhi De
Published: March 2013

5wt%B2O3-doped (Li,K,Na)NbO3 (abbreviated as LKNN-B5)-based lead-free piezoelectric ceramics were prepared via solid state synthesis. The electrical humidity sensitive properties of LKNN-B5 ceramics were examined and compared with pure LKNN ceramics. The results revealed thatB2O3 doping enhanced electrical stability of LKNN-based ceramics in relative humidity (RH) range of 33-95%. The capacitance change was suppressed from 105% down to 43% when doped with B2O3. The average absorption time was reduced from 5.5 min to 1.5 min, and desorption time decreased from 8.5 min to 2.0 min. The enhanced electrical stability of LKNN-B5 series was attributed to the dense structure induced by liquid phase sintering.
Effect of Sheet Nanocarbon on Properties of Low Carbon Al2O3-C Refractories
Authors: Wu Xiao Xian , Li Hong Xia , Liu Guo Qi , Niu Chong Chong , Ma Tian Fei
Published: March 2013

Sheet nanocarbon-Al2O3 composite powders were produced by vibratory milling using expanded graphite and Al2O3 powders as raw materials. The effect of different vibratory milling time on phase compositions and microstructure of the composite powders were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM). Then sheet nanocarbon-Al2O3 composite powders were used as additives to produce low carbon Al2O3-C refractories which had a carbon content of 6%. The results showed that about 50nm thickness sheet nanocarbon and Al2O3 composite powders were produced via 15h milling with expanded graphite to Al2O3 powders weight ratio of 1:2. With the increasing of milling time, the (002) diffraction peaks of graphite wear off gradually and nanosheet was desquamated from expanded graphite; It is beneficial to improve the bulk density, cold modulus of rupture (CMOR) and thermal shock resistance of Al2O3-C refractories when adding certain sheet nanocarbon-Al2O3 composite powders. The sample containing 0.5% sheet nanocarbon had a CMOR of 18.51MPa after 1000 °C heat processing in N2 atmosphere, while sample without adding any sheet nanocarbon was only 12.35MPa; The residual cold modulus of rupture (CMORTS) of sample containing 1% sheet nanocarbon was 4.22MPa after thermal shock test, while that of sample without nanocarbon was only 2.18MPa.
Mechanical Properties of AlMgB14-xTiB2 Prepared by Field Activated and Pressure Assisted Synthesis
Authors: Miao Yang , Liu Wen , Zhuang Lei , Cheng Hui Ling , Meng Qing Sen
Published: March 2013

In this paper, Mechanical alloying (MA) and field activated and pressure assisted synthesis (FAPAS) were used for preparing the ultra-hard, super-abrasive AlMgB14-xTiB2 composite ceramic. The samples were fabricated at 1500 under a pressure of 60 MPa. The microstructures and compositions of samples were observed and determined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD). It was indicated that addition of TiB2 was effective for increasing both quantities. A maximum Vichers hardness of 38.5GPa and a fracture toughness of 3.85MPam½ of AlMgB14 reinforced with 70 wt.% of TiB2 were achieved. Abrasion wear tests showed that adding TiB2 would improve the wearability obviously.
Energy-Storage Study in Lead-Free Anti-Ferroelectric Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 Ceramics
Authors: Gao Feng , Dong Xian Lin , Mao Chao Liang , Cao Fei , Wang Gen Shui
Published: March 2013

Lead-free (1-x-y)Bi0.5Na0.5TiO3-xBaTiO3-yK0.5Na0.5NbO3 (BNT-BT-KNN) ceramics were fabricated by traditional sintering method. The X-ray diffraction patterns showed that the ceramics are all crystallized into a perovskite structure phase. Measurements of temperature-dependent dielectric constants showed the two typical shoulders observed in the BNT-BT binary system, indicating that the ceramics are also of relaxor anti-ferroelectric nature. Moreover, it was observed that the dielectric constants decreased sharply with the increase of KNN addition, while maintained the same level when the BNT/BT ratio changed. The P-E hysteresis loops showed that the saturated polarization and the remnant polarization both decreased with the increasing addition of KNN, while the reduction of the BNT/BT ratio enhancesd the saturated polarization. The energy-storage density calculated from the P-E loops also increased with the decrease of KNN addition and BNT/BT ratio, which further demonstrated that the key for improving the energy density of BNT-BT-KNN ceramics is relatively low addition of KNN and low BNT/BT ratio.
Fabrication and Mechanical Properties of SiC/Cu Composites with Zn Addition by Hot Pressing Sintering
Authors: Liu Huang , Luo Guo Qiang , Chen Pin Gan , Shen Qiang , Zhang Lian Meng
Published: March 2013

SiC/Cu composites exhibit low density, low coefficient of thermal expansion and excellent mechanical properties. In this study, Zn of 2 wt. % was added as the sintering activator, and the high volume faction (60%) SiC/Cu composites was fabricated by hot pressing sintering technology. The phase composition and morphology of as-prepare samples were characterized by X-ray diffraction (XRD) system and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) system. The as-prepared SiC/Cu composites were dense and uniform as well as void free. The results show that SiC/Cu composites can reach excellent mechanical properties of SiC/Cu composites. With the increase of sintering temperature, Vickers hardness and the bending strength of the samples increased obviously and the as-prepared SiC/Cu composites achieved a maximum Vickers hardness and bending strength respectively of 195MPa and 140MPa.
Investigation of Viscosity Measurements of Molten Cu-Zr-Al Alloys
Authors: Zhou Chao , Hu Li Na
Published: March 2013

Viscosity reflects kinetic behaviors of metallic glass liquids, as well as the changes of structures of liquids with temperature. In the present work, the viscosity of superheated Cu-Zr-Al alloys has been detected by a torsional oscillating viscometer, and the experimental parameters have been explored. The experimental results indicate that Cu-Zr-Al alloys react with corundum crucibles and are not oxidated easily in the viscometer. In addition, the influence of thermal history on viscosity measurements is not inconsiderable. By eliminating the above factors, an abnormal three-stage trend of viscosity changes is observed finally. Analysis shows that this abnormal dynamic phenomenon probably is attributed to the transition of clusters in different temperature ranges of the glass liquids, and might correspond to the abnormal thermodynamic behavior observed in Cu-Zr-Al liquids.
Critical Cooling Rate for the Glass Formation of Fe80-XCoxP13C7 Alloy
Authors: Xu Kai , Wang Yan , Li Qiang
Published: March 2013

In this work, the critical cooling rate Rc for glass formation of a series of Fe80-xCoxP13C7 (x = 0, 5, 10, 15, 20 at.%) alloys was determined by means of constructing CCT curves using Uhlmanns method. The calculated critical cooling rates for x = 0, 5, 10, 15, 20 at.% are 621, 441, 548, 894, 922 K/s, respectively. These results well coincide with the maximum diameters of Fe80-xCoxP13C7 amorphous alloys determined by experiments varying with the content of Co. The calculated Rc was also on the reasonable order of magnitudes. In addition, the values of three common GFA criterions of Trg, ΔTx and γ were calculated according to the thermodynamic data determined from DSC and DTA curves of Fe80-xCoxP13C7 (x = 0, 5, 10, 15, 20 at.%) bulk amorphous alloy. The validity of these GFA criterions in the series of Fe80-xCoxP13C7 (x = 0, 5, 10, 15, 20 at.%) alloys were investigated and it was pointed out that these three GFA criterions were not able to explain the experimental results of the maximum diameters of Fe80-xCoxP13C7 amorphous alloys varying with the content x of Co.
Deformation Micromechanisms of a Ti-Based Metallic Glass Composite with Excellent Mechanical Properties
Authors: Bai Jie , Li Jin Shan , Kou Hong Chao , Wang Peng , Wang Jun , Tang Bin , Zhong Hong
Published: March 2013

A Ti-based metallic glass composite with composition of Ti48Zr20Nb12Cu5Be15 exhibits good ambient plasticity in tensile and compressive loading. The macro and micro mechanisms during deformation have been investigated systematically. Obvious asymmetry between the tensile and compressive properties of the composite has been observed, indicating amorphous matrix effect on the metallic glass composite. The micro fracture mechanism of dendrites in compression can also be attributed to two mechanisms: shear induced fracture in major and tension induced fracture in local, revealing a constraint of matrix induced complex stress state in composite. Pile-ups of dislocations in dendrites cause work-hardening of composite, and the impedance of dendrites to shear bands is responsible for the improvement of plastic strain.
Microstructure Evolution of TiAl under Tensile Impact Loadings
Authors: Zan Xiang , Ouyang Li , Wang Yu , He Yue Hui , Liu Yong , Song Wei Dong
Published: March 2013

The microstructure evolution of TiAl intermetallics with different microstructures loaded under different strain rates and temperatures was investigated. The results showed that the deformation twinning dominated the deformation process under high strain rate, while dislocation slip was another dominating deformation mode under quasi-static loadings. The proportion of twinned grain increased with the increased strain rate. In Duplex TiAl, the plastic deformation was mainly found in equaxied grains and seldom found in lamellar grains.
Experimental Research on the Friction and Wear Properties of Ni-Based Composite Coating Prepared by Laser Cladding
Authors: Chen Shu Fa , Feng Cheng Long , Yang Jin , Chen Jin Song
Published: March 2013

In this study, the dry sliding wear behavior of Ni-based self-lubricating wear-resistant coating was characterized under various loads at 300 . Morphologies and compositions of the worn surface were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The experimental results showed that with the increase of load, both the frictional coefficient and wear rate decreased firstly, then slightly increased. A small amount of debris dispersed on the worn surface of the coating under low load (2 N). Since the effects of oxide layer and lubricant particles spreading onto the worn surface, the coating exhibited superior friction, and improved the wear properties under moderate load (5 N). As the load further increased, till up to 10N, the worn surface started to appear some shallow grooves and craters. This was contributed to the dispersion of carbides and lubricant particles.
Effect of Heat Treatment on the Structure and Properties of EW75 Magnesium Alloy Plate
Authors: Qu Juan , Zhang Kui , Ma Ming Long , Li Yong Jun , Li Xing Gang
Published: March 2013

In this study, Mg-7Gd-5Y-1Nd-0.5Zr alloy (EW75) was produced by melting method and then press-forged into large size plate. The properties of the Mg-7Gd-5Y-1.2Nd-0.5Zr alloy were optimized through T6 heat treatment. The microstructures of alloy were observed by means of optical microscopy (OM), scanning electron microscopy (SEM). Its mechanical properties under different heat treatment conditions were determined by tensile tests. The results indicated that increasing the solid solution temperature and prolonging the solid solution time can both lead to the dissolution of second phase in the alloy back into the matrix. The solid solution temperature affects the dissolution process more than the solid solution time. Grain growth occurred during the solid solution process. The grain size of the matrix enlarges with the increase of solid solution temperature. The tensile test result showed that the tensile strength of the alloy was significantly improved after T6 heat treatment. Its tensile strength in the same direction was nearly 40% up after T6 heat treatment. The analysis shows that T6 heat treatment can effectively eliminate the larger deformed precipitates and beneficial to the formation of hard precipitates, which leads to an improvement in the alloys tensile strength.
Microstructure and Properties of MAO Coatings for AZ91D Magnesium Alloy in Varies Work Mode
Authors: Cui Xue Jun , Lin Xiu Zhou , Liu Chun Hai , Yang Rui Song , Li Ming Tian
Published: March 2013

Micro arc oxidation coatings were prepared on AZ91D magnesium alloy in order to evaluate the role of electrical parameters under different work mode. Taking HV hardness and pit corrosion time as investigation index, the optimum process parameters were obtained through orthogonal experiment method. The morphology of coating was observed by scanning electron microscopy (SEM). The results showed that the coatings with dense and few micro pores can be obtained under constant current and power mode, and this kind coatings are of good corrosion resistance and have HV micro-hardness compared with those under constant voltage mode.
Effect of Aging Temperature on Microstructure and Mechanical Properties of AZ81-4%Gd Magnesium Alloy
Authors: Guo Quan Ying , Liu Zheng , Mao Ping Li , Sun Jing
Published: March 2013

The microstructure and mechanical properties of AZ81-4%Gd magnesium alloy sheet after aging at 150, 200, 250, 300 were analyzed and tested by x-ray diffraction,scanning electron microscope,energy dispersive spectrometer and hardness tester. The results demonstrated that β-Mg17Al12 phases were precipitated in two patterns, those were continuous precipitation and discontinuous precipitation during aging below 250 and the morphology of β-Mg17Al12 phase was different. The β-Mg17Al12 phases were precipitated in the pattern of continuous during aging at 300. The analysis showed that the precipitation pattern and morphology of β phases were related to the mechanism of nucleation and growth. The alloy hardness achieved the highest value after aging at 250 and 300 for 24 hours, the hardness of the alloy was the highest after aging at 150 and 200 for 32 hours. In addition, the observations on microstructure and the testing on hardness revealed that the best aging temperature is 200 for the AZ81-4%Gd alloys within the scope of the study.
Microstructure and Corrosion Resistance of AZ80/Al Composite Plate Fabricated by Friction Stir Processing
Authors: Liu Fen Cheng , Liu Qiang , Huang Chun Ping , Yang Kun , Yang Cheng Gang , Ke Li Ming
Published: March 2013

AZ80/Al composite plate was fabricated by means of friction stir processing (FSP) aimed at the improvement of corrosion resistance of magnesium alloy. The cross-section microstructure, surface morphology and corrosion resistance of the Al composite layer were investigated. The experiment results indicated that a dense composite Al layer with superfine and uniform grains was formed, and a few amount of intermetallic compounds existed in the area of Mg/Al interface. The bonding strength of AZ80 magnesium alloy substrate and 1060 pure Al layer was proved to be high which was resulted from the metallurgical bonding of FSP. Microhardness measurement showed the continuous changing of microhardness values from the outmost surface of composite Al layer to the magnesium alloy substrate. Results of electrochemical corrosion test of the composite plate in 5 wt.% NaCl solution showed the better protection effect of the composite Al layer on the magnesium alloy in a corrosion medium. Almost the same corrosion level on the whole corrosion surface was observed which indicated the highly uniform microstructure of the composite layer. It was also proved that the plain arches on the outmost surface of the composite Al layer had no influence on the corrosion resistance of composite Al layer.
Isochronal Aging Hardening of the Mg-8Gd-3Y-0.5Zr Alloy after Cold Rolling
Authors: Xie Yan Cai , Li De Jiang , Zeng Xiao Qin , Su Xin , Ding Wen Jiang , Chen Bin
Published: March 2013

By transmission electron microscopy (TEM) and optical microscopy (OM), the isochronal aging hardening law and microstructure have been studied for the Mg-8Gd-3Y-0.5Zr alloy after cold rolling. During isochronal aging process (heated from room temperature to 500 with the heating rate of 1/min), there are two peak hardness temperature points, which are corresponding to the large number of precipitation of β and β phases, and the peak aging time of the alloy substantially decreased with the increase of deformation reduction. The β phases started to precipitate at temperatures of 145, 134, 127 and 124 in the alloy after cold rolling with the reduction of 0%, 8%, 15% and 22%. The heating rate greatly affected the starting precipitation of metastable phases. β phases started to precipitate at temperatures of 109 and 124 with the reduction of 22% and with the heating rates of 3 /min and 30 /min.
Effects of Texture on Tensile Property of Extruded AZ31 Magnesium Alloy Investigated by Acoustic Emission
Authors: Sun Chuan Kai , Luo Hong Yun , Han Zhi Yuan
Published: March 2013

In this paper, effects of texture on tensile property of extruded AZ31 magnesium alloy are investigated by acoustic emission (AE). The results show that the extruded AZ31 magnesium alloy used in this research has the strong texture of and tensile anisotropy. The yield strength of TD-sample is about 80MPa, which is half of that of ED-sample. AE results show that the AE count of the TD-sample is higher than that of the ED-sample. These AE results suggest that there are more deformation twins in the TD-sample than in the ED-sample. It can be concluded that the deformation twinning can strongly influence the anisotropy, which is mainly due to the flow stress relief induced by twinning and the interaction of twins and dislocations during the strain hardening.
Rolling Temperature and Subsequent Annealing on Microstructure, Texture and Mechanical Properties of Consecutive Rolled Mg-2.0Zn-0.8Gd Alloy
Authors: Yan Hong , Chen Rongshi , Han En-Hou
Published: March 2013

Mg-2.0Zn-0.8Gd (wt. %) alloy was rolled consecutively at different temperatures. The influence of rolling temperature and annealing process on the microstructure, texture and mechanical properties of the sheet were investigated. A deformation microstructure consisting of many intersected twins and a few dynamic recrystallization grains, and a basal texture with basal poles tilting about ± 10-15° from the normal direction towards the rolling direction were observed in the as-rolled sheet after 4 consecutive rolling processes. Static recrystallizaiton took place in the sheet after annealed above 300 °C. The annealed sheet exhibited a uniform microstructure and a non-basal texture with basal poles tilting about ± 38-43° from the normal direction towards the transverse direction. The annealed sheets exhibited higher ductility about 32% along the rolling direction and 40% along the transverse direction comparing with the as-rolled sheets. The static recrystallization during annealing process was helpful to modify the texture as well as the dynamic recrystallization during rolling in the RE-containing alloys.
Microstructure and Mechanical Properties of Backward-Extruded Mg-Zn-xCa Biomaterials
Authors: Li Xue Jun , Li Hui , Zhao Shuang Shuang , Ma Ning , Peng Qiu Ming
Published: March 2013

The Mg-1.0Zn-xCa (x=0.2, 0.5, 0.8, 1 wt. %) alloys were prepared by zone solidification and backward extrusion technology. The microstructure and mechanical properties of backward-extruded Mg-1.0Zn-xCa alloys were investigated. The results showed that these backward-extruded Mg-1.0Zn-xCa alloys were mainly composed of equi-axed pentagon-shaped grains and some Mg0.9Zn0.03 precipitates. The tensile and compressive strengths of backward-extruded Mg-1.0Zn-xCa alloys were greatly improved. The improved mechanical properties are mostly attributed to fine grain strengthening, solid solution strengthening and precipitate strengthening. The results demonstrated that the micro alloying of Ca element was one of effective method to improve the mechanical properties of Mg-1.0Zn based biomaterials.
Detection and Deformation Mechanism of Non-Metallic Inclusions in FGH96 Alloy Isothermal Forging Disk
Authors: Wang Xiao Feng , Zhou Xiao Ming , Yang Jie , Zou Jin Wen , Wang Wu Xiang
Published: March 2013

According to the defects of powder metallurgy superalloy, especially the influence and damage of inclusions on properties of disk, the deviation between nondestructive testing and metallographic testing of inclusions in FGH96 alloy isothermal forging disk was investigated. Meanwhile, the types and deformation mechanism of inclusions were studied. The results showed that the buried depth tested by metallographic detection was less 67-180μm than nondestructive testing. The size of inclusions with metallographic detection was less about 18-50μm than nondestructive testing. The major types of inclusions in practical disk were Al2O3 and Al2O3-SiO2, the inclusions run through several grains, no matter Al2O3 or Al2O3-SiO2. The Al2O3 inclusion and matrix was purely mechanical bonding, but the Al2O3-SiO2 had reaction zone. There was remarkable effect of extrusion process on crushing and dispersing Al2O3 inclusion, but which was unremarkable for Al2O3-SiO2.
A New Deformation Region and How Low Do You Go? – "Intrinsic Deformation Limit"
Authors: Shen Jun Jie , Ikeda Kenichi , Hata Satoshi , Nakashima Hideharu
Published: March 2013

The creep deformation in pure aluminum was investigated using helicoid spring samples at room temperature, 298 K, and σ < 1.19 MPa. It was found that the stress exponent is n = 0, which means the creep behavior in this region is independent on applied stress but some physical properties of materials. The creep behavior was suggested to be controlled by surface diffusion based on the strongly effect of surface area on creep behavior only in this creep region (n = 0). The threshold creep rate, , called intrinsic deformation limit, decided by surface diffusion was suggested. This discovery provided a new perspective to understand the extremely slow deformation in the nature.
Effect of Alloy States on the Recrystallization Behavior in Single Crystal Superalloy
Authors: Liu Li Rong , Huang Jing Sheng , Zu Guo Qing
Published: March 2013

Recrystallization behavior after indentation loading and heat treatment at different temperatures of the as-cast and solution-treated alloy was investigated. The results showed that slip deformation occurred in the as-cast and heat treated samples after deformation and apparent slip line can be observed. Slip lines of heat treatment state was significantly more than that of the as-cast samples. Neither equiaxed nor cellular recrystallization occurred in the surface of the as-cast and solution-treated samples after heat treatment at 1120; Slip traces were examined in the vicinity of indentation and M6C carbide precipitated on the slip line in heat-treated samples, while cellular recrystallization occurred in the internal part and MC carbides became the nucleation centers. Equiaxed recrystallization occurred simultaneously in samples of the two states with the heat treatment at 1310 after deformation and the recrystallization area increased with the processing time; after heat treatment with same time and temperature, recrystallization area of the cast samples were less than that of heat-treated samples.
Mechanical Properties and Microstructure of Nb/Nb5Si3/Cr2Nb Alloys Prepared by Spark Plasma Sintering
Authors: Zong Wei , Liu Wei , Sha Jiang Bo
Published: March 2013

Through the spark plasma sintering technology (SPS), the Nb/Nb5Si3/Cr2Nb mixed powders with different volume ratios of 7:1:2 and 7:2:1 were sintered into ingots. The effects of three powder mixing methods on phase constitution, microstructure and room-temperature mechanical properties of the ternary Nb/Nb5Si3/Cr2Nb alloys were investigated. The result shows that the method of dry mixing without ball milling is advantageous for toughness, the increase of SPS temperature decreases the toughness whereas improves the hardness. The stiffening Nb5Si3 and Cr2Nb phases tend to form a continuous network, resulting in decrease of toughness. It is interesting that when the fractions of the Nb5Si3 phase larger than that of the Cr2Nb phases, these strengthening phases prefer to appear in the form of network, which is detrimental for toughness.
Effect of Hot Isostatic Pressing on the Microstructure of Single Crystal Ni-Based Superalloy DD10
Authors: Liu Li Jun , Xue Ming , Chen Jing Yang , Cao La Mei
Published: March 2013

The effects of hot isostatic pressing on the microstructures of a third generation single crystal Ni-based superalloy DD10 were investigated by using optical microscope (OM), scanning electron microscope (SEM), electron microprobe analyzer (EPMA). The results showed that the micropores in the interdendritic region were eliminated completely after hot isostatic pressing at 1320 and 150MPa. Meanwhile, the morphology of γ precipitates changed to be more cuboidal and the distribution of γ precipitates in both dendrite core and interdendritic region became more uniform after hot isostatic pressing. Hot isostatic pressing also promoted the homogenization of the composition between dendrite core and interdendritic region and the dendritic segregation of Re, W, Al and Ta was decreased.
Effects of Ruthenium on Microstructure and Stress Rupture Properties of a Nickel-Base Single Crystal Superalloy
Authors: Yang Shuai , Zhang Jian , Luo Yu Shi , Zhao Yun Song , Tang Ding Zhong , Cao Guo Qiang
Published: March 2013

The effect of Ru addition (0 wt.%, 3 wt.%, 5 wt.%), on γ morphology, elemental segregation, microstructural stability under long-term thermal exposure at 980 and stress rupture properties at 1100°C/130MPa have been studied. The results showed that with the increase of Ru content, the γ/γ eutectic volume fraction and the dendrite arm spacing decreased gradually. The γ' phase mean size in three alloys decreased with the increase of the Ru content. On the other hand, the dendrite segregation of Al, Ta towards interdendrite area and ReW towards dendrite core area was alleviated gradually with the increase of the Ru content. The increase of Ru content from 0 wt.% to 5 wt.% pronouncedly enhanced the stress rupture properties by suppressing the precipitation of TCP phases effectively at high temperature.
Investigation on Creep Mechanism of a Ni3Al-Based Single Crystal Superalloy IC6SX under 760°C/540MPa
Authors: Jiang Li Wu , Li Shu Suo , Wu Mei Ling
Published: March 2013

The creep behaviors of a Ni3Al-base single crystal superalloy IC6SX prepared by spiral grain selection method was studied systematically under the testing condition of 760/540MPa. The microstructure evolution, movement of dislocations, formation of the dislocation networks and dislocation configuration during the creep process were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the creep performance of the single crystal alloy IC6SX is excellent under 760/540MPa. The experimental results showed that the creep curve of the Ni3Al-base single crystal superalloy IC6SX was divided into three stages, including decelerating creep stage, steady-state creep stage and accelerated creep stage. The microstructure and the dislocation configuration were different at different stage during the creep and the raft microstructure has not been formed. The creep mechanism was main slipping characterized by dislocation glide mechanism.
Preliminary Research on a New Ultra-High Strength Titanium Alloy
Authors: Qu Heng Lei , Zhao Yong Qing , Zhu Zhi Shou , Li Hui , Feng Liang , Zhou Lian , Li Ming Qiang
Published: March 2013

Some research results are introduced briefly in this paper. A new kind of titanium alloy was designed based on nine elements system, which belongs to (a+b) type. Bars with diameter of 14 mm were produced via Vacuum Arc Remelting (VAR) melting and conventional forging and rolling facilities. Influence of alloy elements contents and heat treatments on microstructure and mechanical properties of the new alloy were studied. The results show that Ultimate Tensile Strength (UTS) is about 1200~1700MPa and Elongation (EL) is normally less than 5% at R.T., though Electron Beam (EB) welding can be proceeded, but the toughness of the alloy is poor at R.T.High temperature (HT) short-term strength of the alloy is also acceptable up to 600. Based on the above performances, the new material can be applied in the corresponding circumstances.
Relationships between Spring-Back and Microstructure of Ti-15V-3Cr-3Sn-3Al Titanium Alloy Sheet during Bending Process
Authors: Li Lin Lin , Wu Guo Qing , Liu Chang Xu , Sha Ai Xue
Published: March 2013

Evolutions of microstructure, micro-hardness in the central deformation area and spring-back, were studied in different bending conditions of Ti-15V-3Cr-3Sn-3Al titanium alloy sheet. The results show that, with the increase of bending deformation, i.e. increase of bending angle or decrease of bending radius, the grain area, the grain feret diameter ratio and micro-hardness in the central deformation area all show nearly linear growth trends. The spring-back angle has no clearly correlation with the degree of bending deformation. While the spring-back rate correlates positively with the length of deformation-affected zone, which can reflect the characteristics of bending deformation more intuitively than that of spring-back angle.
Microstructural Evolutions of a High Temperature Titanium Alloy Processed by Thermal Mechanical Treatments
Authors: Wang Tao , Guo Hong Zhen , Yao Ze Kun , Zhao Zhang Long , Fu Shu Hong , Zhang Yong
Published: March 2013

TG6 alloy is a new titanium alloy which has been designed to reach the service temperature of 600°C. The microstructural evolutions of TG6 alloy under different thermal mechanical treatments were studied. It was found that lamellar microstructures with basketweave α lamella are obtained for TG6 alloy forged in β field. The evolution mechanism is transformed from dynamic recrystallization to dynamic recovery and the thickness of α lamella increases with increasing forging temperature. The aspect ratio of α lamella decreases firstly and then increases with increasing deformation degree. Grain boundary α lath appears when the deformation degree is less than 40%. The thermal mechanical treatments, including deformation in β field firstly and then deformation in α+β field result in the transformations of the microstructures drastically. The deformation degree in α+β field decides the final microstructure. The deformation degree of 20% in α+β field results in partial globular α phase.
Effect of Sputtering Current on Growth and Microstructure for Titanium Alloy Coatings onto SiC
Authors: Huang Hao , Wen Mao , Wang Min Juan , Li Zhen Xi , Huang Xu , Xie Chuan
Published: March 2013

The influences of sputtering current on deposition rate, composition, microstructure evolution and growth mechanism for titanium alloy coatings onto SiC fibers are explored by surface profiler, auger electron spectrometer, X-ray diffraction, scanning electron microscopy and atomic force microscope. The experimental results show that crystallization take place in all coatings with hexagonal structure (α-Ti). As sputtering current is increased, deposition rate and Al content increase, and Ti content decreases. Coating growth mode alsotransforms from V-shaped column grains to equiaxed grains as sputtering current increased. The column grains are generally not single grains, and more nanograins are composed
Effect of Strontium and T6 Heat Treatment on Structure and Performance of Al-11.6Si-0.5Mg Alloy
Authors: Lin Ji Xing , Zhang Jun Ping , Niu Li Yuan , Sun Da Ren , Shi Zi Mu , Li Yong , Li Guang Yu
Published: March 2013

In this study, Strontium (Sr) was added as modifier during the casting of Al-11.6Si-0.5Mg alloy, and the effect of T6 heat treatment on microstructure and performance of alloy was also investigated. The results showed that the 0.3% Al-8%Sr master alloy can refine effectively the α-Al dendrite and eutectic structure; the best economic process of T6 heat treatment is solution at 535°C for 6 hrs., and water cooling at 50~60°C,aging at 160°C for 6 hrs , then air cooling. After Sr modification and T6 heat treatment, the mechanical properties of alloy are improved remarkably, i.e., the tensile strength increased to 348MPa from 183MPa before modification and the elongation raises from 3.0% to 6.5%. So this alloy is applied to the strain clamp products in electric power fitting industry.
Effect of Compound Fluxes on A-TIG Welding Joint Depth of Cu-Cr-Zr Alloy
Authors: Jiang Wen Hong , Yu Ran Dong , Lu Sheng
Published: March 2013

A-TIG welding for Cu-Cr-Zr copper alloy was carried out on the eleven pure surface activating fluxes including oxides, fluorides and chlorides on the welding formation and the weld D/W ratio by the means of super depth of field and metallurgical microscope. It was found that the oxides and fluorides could improve welding penetration remarkably, especially with CaF2,ZnF2,SiO2 andCr2O3. Four compound fluxes were chosen from the eleven pure surface activating fluxes, which could increase the penetration and modify the welding shape. An optimized formula composed of the four compounds (CaF2,ZnF2,SiO2 and Cr2O3) was developed by using the formula of uniform design method. It showed that the optimized formula could reach a good weld ability and its weld penetration was 2.5 times more than that of TIG.
Magnetic Properties and Morphology of the Cobalt Particles Prepared in Different Liquid Solvent
Authors: Huang Xue Min , Wang Quan Sheng , Liu Ying , Zhao Xiu Chen , Wen Shu Lai
Published: March 2013

The two kinds of flower-like ultrafine cobalt particles were prepared by reducing cobalt chloride (CoCl2·6H2O) with hydrazine hydrate (N2H4·H2O) under ultrasonic and microwave radiation, in which ethanol-water or ethylene glycol-water mixture was used as solvent. The morphology, crystal structure and magnetic properties of the as-prepared particles were characterized by scanning electron microscope (SEM), x-ray diffraction pattern (XRD) and vibrating sample magnetometer (VSM). The results show that the petals of the flower-like cobalt particles prepared in the ethanol-water system were dendritic, while the petals of the flower-like cobalt particles prepared in the ethylene glycol-water system were sword-like. The crystal structure of cobalt particles prepared in the two kinds of systems both consisted of hexagonal close-packed cubic phase and face-centered cubic phase, but the relative content was different. The saturation magnetization of the cobalt particles with dendritic petals and the cobalt particles with sword-like petals was the same approximately, but their coercivity was greatly different (the difference in value about 7184.14Am-1), which might be attributed to the magnetocrystalline anisotropy and shape anisotropy.
The Surface Heat Transfer Coefficient Model of 7075 Al-Alloy Extrusion Product and its Temperature Prediction
Authors: Hou Wen Rong , Ji Wei Bing , Zhang Zhi Hao , Xie Jian Xin
Published: March 2013

Surface heat transfer coefficient is a key parameter for accurately predicting the extrusion product temperature near the die exit and then achieving isothermal extrusion by speed controlling. Based on the heat transfer characteristics of extrusion product during cooling process, a dynamic loading method of heat transfer boundary conditions was proposed. The surface heat transfer coefficient model of 7075 Al-alloy extrusion product was established using the dynamic loading method and inverse calculation comprehensively. The model indicated the relationship among surface heat transfer coefficient h, surface temperature T and initial temperature T0 as h=1.16T-0.97T0. Its accuracy is high enough for calculating the surface temperature of 7075 Al-alloy extrusion product. According to the model and the experimental data, the relationship between the product and the measured temperatures can be established. It provides an effective way to solve the problem that the extrusion product temperature near the die exit cannot be directly measured.
Thermal and Optical Properties of High Refractive Index xNb2O5-(1-x)La2O3 Glasses Prepared by Aerodynamic Levitation Method
Authors: Cheng Yu Xing , Xu Gui Sheng , Yu Jian Ding , Pan Xiu Hong , Zhang Ming Hui , Liu Yan
Published: March 2013

Bulk glasses of xNb2O5(1-x)La2O3(NL) with high refractive index were prepared by aerodynamic levitation method. Only when x ranges from 0.62 to 0.72, NL glasses can be obtained. The effect of compositions on the thermal property and refractive index was investigated. The results indicated that the glass transition temperature ranged from 733 to 767 with the increasing of La2O3in NL glasses, while the crystallization peak ranged from 811 to 837 . The glasses had high refractive index ranging from 2.26 to 2.31. According to the Drude-Voigt relationship, the Abbe number of the glasses was calculated to be about 20. This type of glass was colorless and transparent in the region from visible to infrared region. Thus, the niobate glass system has promising application in lenses, next-generation optical disk, and endoscopes.
The Metal Flowing Behaviors and Die Bearing Band Optimization of a Large Al-Alloy Extrusion Profile
Authors: Huang Dong Nan , Ning Yu , Shao Fang Lei
Published: March 2013

In this paper, in order to optimize the extrusion die action and to control quality of an industrial large Al-profile, the effects of die bearing band on the metal flowing behaviors are analyzed by applying some special methods, including designing the bearing band of the die as inclined plan and designing the geometry model as detachable structure. The velocity field showed that the metal flowing velocities in central and left-side locations were higher than that in groove location. The reasonable size-configuration of the extrusion die bearing band was obtained, and the defect of the right-direction bending was able to be removed effectively. The inclined bearing band structure, detachable geometry model and configuration method based on velocity balance proposed in this paper provided a valuable reference to design and to optimize this kind of solid Al-alloy large profile.
Investigation on the Preparation and Properties of MoCu Gradient Material
Authors: Yang Xiao Hong , Zhang Ni Na , Xiao Peng , You Cai Yin
Published: March 2013

In this study, MoCu gradient materials were prepared by the combination methods of liquid phase sintering and permeability copper. The effect of pressure and sintering temperature on the properties of MoCu gradient materials was studied. The physical and mechanical properties of MoCu20/MoCu40 and MoCu20/MoCu30/MoCu40 gradient materials were tested respectively. The results showed that the relative density of green compact and sintered gradient materials increased with the increase of pressing force from 10 tons to 30 tons. The electrical conductivity and hardness of sintered compact achieved the maximum value by the 20 tons. Within the sintering temperature range of 1100 to 1400, the relative density, electrical conductivity and hardness of sintered gradient materials increased with the increase of sintering temperature. The overall properties of sintered materials were obtained at 1350. For two-layer and three-layer MoCu gradient materials, their microstructures and chemical compositions showed a continuously and gradient change. The bending strength and the thermal conductivity of three-layer MoCu gradient materials were better than that of two-layer gradient materials.